Inverted pendulum type vehicle

ABSTRACT

An inverted pendulum type vehicle having a tiltable rider mounting section includes a first travel operation unit and a second travel operation unit, which are disposed with an interval provided therebetween in the longitudinal direction and which are capable of traveling in all directions. In a situation wherein a predetermined representative point of the vehicle or the first travel operation unit is to be moved rightward or leftward, the traveling operations of the first travel operation unit and the second travel operation unit are controlled such that the travel velocity of the first travel operation unit and the travel velocity of the second travel operation unit in the lateral direction are different from each other so as to cause the vehicle to turn about a turn center at the rear of a ground contact point of the first travel operation unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inverted pendulum type vehiclecapable of traveling on a floor surface.

2. Description of the Related Art

There has conventionally been known an inverted pendulum type vehicle inwhich a rider mounting section tiltable relative to the verticaldirection is attached to a base body, to which a travel operation unitthat travels on a floor surface and an actuator that drives the traveloperation unit are installed. The inverted pendulum type vehicle isconfigured to control the traveling motion of the travel operation unitby moving the supporting point of the inverted pendulum thereof.

In, for example, Japanese Patent Application Laid-Open No. 2011-068165(hereinafter referred to as Patent Document 1), an inverted pendulumtype vehicle in which a travel operation unit is driven according to thetilt or the like of a rider mounting section thereby to permit travel ona floor surface in all directions, including the longitudinal directionand the lateral direction relative to a rider, has been proposed by theapplicant of the present application.

The conventional inverted pendulum type vehicle disclosed in PatentDocument 1 enables the rider to turn the vehicle by moving his/her upperbody so as to gradually change the traveling direction of the vehicle.Generally, however, the rider is required to have a high steering skillto accomplish a smooth turn.

Especially when the vehicle is traveling forward at a low velocity orwhen the vehicle has almost come to a stop, turning the vehicle, i.e.,changing the direction thereof, has been difficult for even a skilledrider.

SUMMARY OF THE INVENTION

The present invention has been made with a view to the backgrounddescribed above, and an object thereof is to provide an invertedpendulum type vehicle, the maneuverability of which has been improved topermit an easier turn of the vehicle.

To this end, an inverted pendulum type vehicle in accordance with thepresent invention has at least: a first travel operation unit capable oftraveling on a floor surface; a first actuator that drives the firsttravel operation unit; a base body to which the first travel operationunit and the first actuator are installed; and a rider mounting sectionattached to the base body such that the rider mounting section istiltable relative to a vertical direction, wherein the first traveloperation unit is configured to be capable of traveling in alldirections, including a longitudinal direction and a lateral directionrelative to a rider on the rider mounting section, by a driving force ofthe first actuator, the inverted pendulum type vehicle furtherincluding:

a second travel operation unit, which is connected to the first traveloperation unit or the base body with an interval provided from the firsttravel operation unit in the longitudinal direction and which isconfigured to be capable of traveling in all directions on a floorsurface;

a second actuator which generates a driving force for causing the secondtravel operation unit to travel at least in the lateral direction; and

a control unit, which controls the first actuator and the secondactuator so as to cause the first travel operation unit and the secondtravel operation unit to carry out travel motions thereof according toat least the tilt of the rider mounting section,

wherein the control unit is configured to carry out turning controlprocessing for controlling, through the first actuator and the secondactuator, the travel velocity of the first travel operation unit and thetravel velocity of the second travel operation unit in the lateraldirection to be different from each other so as to cause the invertedpendulum type vehicle to turn about a turn center behind a groundcontact point of the first travel operation unit in a situation in whicha predetermined representative point of the inverted pendulum typevehicle that has been established beforehand or the first traveloperation unit is to be moved leftward or rightward (a first aspect ofthe invention).

According to the first aspect of the invention, the inverted pendulumtype vehicle (hereinafter referred to simply as “the vehicle” in somecases) is provided with, in addition to the first travel operation unitand the first actuator, the second travel operation unit, which isdisposed with the interval provided in the longitudinal directionrelative to the first travel operation unit and which is capable oftraveling in all directions, and a second actuator, which generates thedriving force for causing the second travel operation unit to travel inthe lateral direction.

When the rider on the rider mounting section intends to turn the vehicle(including the changing of the direction), the rider normally attemptsto tilt the rider mounting section by shifting his/her center of gravityrelatively to the right or the left with respect to the rider mountingsection so as to generate a rightward or leftward velocity component ofthe vehicle. In this case, the rider has a tendency to shift his/hercenter of gravity to the right or the left, whichever direction he/sheintends to turn the vehicle. Also in this case, since the rider mountingsection has a tendency to tilt rightward or leftward, the control unitmoves the first travel operation unit rightward or leftward thereby toprevent the rider mounting section from tilting.

Supplementarily, the ground contact portion of the second traveloperation unit hardly supports the gravitational force of the base bodyand the rider combined, so that it would be hardly effective to preventthe rider mounting section from tilting even if the second traveloperation unit is moved rightward or leftward.

Thus, in the situation wherein a predetermined representative point ofthe vehicle, such as a point fixed relative to the base body or therider mounting section, or the first travel operation unit is beingmoved rightward or leftward, it is very likely that the rider is tryingto turn the vehicle to the right side or the left side relative to thevehicle.

Hence, the control unit carries out the turning control processing forcontrolling, through the first actuator and the second actuator, suchthat the travel velocity of the first travel operation unit and thetravel velocity of the second travel operation unit in the lateraldirection are different from each other so as to cause the invertedpendulum type vehicle to turn about the turn center behind the groundcontact point of the first travel operation unit.

This will turn the vehicle due to the difference between the travelvelocity of the first travel operation unit and the travel velocity ofthe second travel operation unit in the lateral direction. In this case,the turn center of the vehicle is located at the rear of the groundcontact point of the first travel operation unit. Therefore, if therider shifts his/her center of gravity to the left side relative to therider mounting section, then the vehicle turns to the left (a turn inthe counterclockwise direction). Further, if the rider shifts his/hercenter of gravity to the right side relative to the rider mountingsection, then the vehicle turns to the right (a turn in the clockwisedirection).

Thus, the inverted pendulum type vehicle according to the first aspectof the invention enables the rider on the rider mounting section to turnthe vehicle in the direction that matches the direction (rightward orleftward) of the motion of his/her body simply by moving his/her body,i.e., tilting the rider mounting section to the right or left, so as tomove the first travel operation unit rightward or leftward.

Consequently, the inverted pendulum type vehicle according to the firstaspect of the invention provides improved maneuverability of thevehicle, permitting easier turning of the vehicle.

In the first aspect of the invention, although the second traveloperation unit may be disposed in front of the first travel operationunit, the second travel operation unit is preferably disposed behind thefirst travel operation unit (a second aspect of the invention).

According to the second aspect of the invention, the magnitude of thelateral travel velocity of the second travel operation unit when thevehicle is turned by the turning control processing can be reduced, ascompared with the case where the second travel operation unit isdisposed in front of the first travel operation unit. This makes itpossible to restrain the occurrence of the slip of the second traveloperation unit and also to reduce the capability required of the secondactuator.

Further, in the first aspect or the second aspect of the invention, itis possible to control the travel velocities of the first traveloperation unit and the second travel operation unit in the lateraldirection such that the position of the turn center, i.e., the relativeposition with respect to the vehicle, is maintained at a fixed position.

However, the control unit is preferably configured to control, throughthe first actuator and the second actuator, the travel velocity of thefirst travel operation unit and the travel velocity of the second traveloperation unit in the lateral direction on the basis of a desired valueor an observed value of the travel velocity in a forward direction ofthe predetermined representative point or the first travel operationunit such that the position of the turn center in the longitudinaldirection is moved toward the front at the rear side of the rider on therider mounting section as the magnitude of the desired value or theobserved value of the travel velocity of the predeterminedrepresentative point or the first travel operation unit in the forwarddirection increases in the turning control processing (a third aspect ofthe invention).

In the present invention, the “observed value” related to an arbitrarystate quantity, such as the travel velocity, means an estimated valuethat has been estimated on the basis of the detection value of the statequantity obtained by an appropriate sensor or an estimated value thathas been estimated from the detection value or values of one or moreother state quantities having certain correlativity to the statequantity according to the correlativity.

According to the third aspect of the invention, the position of the turncenter in the longitudinal direction is shifted closer to a positionimmediately below the rider on the rider mounting section as themagnitude of the desired value or the observed value of the travelvelocity of the representative point (the representative point of thevehicle) or the first travel operation unit in the forward directionincreases when the vehicle is turned by the turning control processing.Hence, it becomes easier to make the position of the rider (the positionprojected onto a floor surface) trace a desired path when the vehicle isturned.

This arrangement makes it easier for the rider to move his/her body tomake a desired turn while moving the vehicle forward.

In the first aspect to the third aspect of the invention, the controlunit is preferably configured to carry out the turning controlprocessing in a situation in which the magnitude of the desired value orthe observed value of the leftward or rightward travel velocity of thepredetermined representative point or the first travel operation unit isa predetermined value or more and to control the first actuator and thesecond actuator such that the travel velocity of the first traveloperation unit and the travel velocity of the second travel operationunit in the lateral direction are the same with each other in asituation in which the magnitude of the desired value or the observedvalue of the travel velocity is smaller than a predetermined value (afourth aspect of the invention).

According to the fourth aspect of the invention, the first actuator andthe second actuator are controlled such that the travel velocity of thefirst travel operation unit and the travel velocity of the second traveloperation unit in the lateral direction become the same with each otherin the situation wherein the magnitude of the desired value or theobserved value of the travel velocity of the predeterminedrepresentative point or the first travel operation unit in the rightwardor leftward direction is smaller than a predetermined value.

This arrangement makes it possible to prevent the vehicle from beingaccidentally turned due to an unintended reel of the body of the riderwhen the rider does not intend to turn the vehicle. In addition, atranslational travel of the vehicle in the lateral direction can bemade, as necessary.

Further, in the situation wherein the magnitude of the desired value orthe observed value of the velocity of the predetermined representativepoint or the first travel operation unit moving rightward or leftward isa predetermined value or more, the turning control processing is carriedout, thus enabling the rider to easily turn the vehicle simply byexplicitly moving his/her body rightward or leftward when turning thevehicle.

In the aforesaid fourth aspect of the invention, the control unitpreferably carries out the turning control processing in a situationwherein the magnitude of the observed value of the leftward or rightwardtravel velocity of the predetermined representative point, which hasbeen set beforehand as a point fixed with respect to the rider mountingsection, is a predetermined value or more (a fifth aspect of theinvention).

More specifically, a tilting motion of the rider mounting section in thelateral direction, i.e., a tilting motion about a longitudinal axis, isgenerated when the rider moves his/her body in the lateral direction.Therefore, the observed value of the velocity of the representativepoint, which has been set beforehand as the point fixed with respect tothe rider mounting section and which is moving rightward or leftward,markedly reflects the motion of the body of the rider in the lateraldirection.

Hence, in the situation wherein the magnitude of the observed value ofthe velocity of the representative point traveling rightward or leftwardis the predetermined value or more, carrying out the turning controlprocessing makes it possible to accurately reflect the rider's intentionwhen turning the vehicle.

In the first to the fifth aspects of the invention, preferably, thecontrol unit is configured to determine a desired value of a turnangular velocity of the inverted pendulum type vehicle on the basis ofat least the desired value or the observed value of the velocity of therightward or leftward travel of the predetermined representative pointor the first travel operation unit and to control the velocities of thetravels of the first travel operation unit and the second traveloperation unit in the lateral direction on the basis of the desiredvalue of the turn angular velocity through the first actuator and thesecond actuator, respectively, in the turning control processing (asixth aspect of the invention).

According to the sixth aspect of the invention, the desired value of theturn angular velocity of the inverted pendulum type vehicle isdetermined on the basis of at least the desired value or the observedvalue of the velocity of the rightward or leftward travel of thepredetermined representative point or the first travel operation unit inthe turning control processing. This arrangement enables the rider tochange the turn angular velocity of the vehicle to a desired turnangular velocity by adjusting the motion of his/her own body in thelateral direction.

In this case, for example, the desired value of the turn angularvelocity is preferably determined such that the magnitude of the desiredvalue increases as the magnitude of the desired value or the observedvalue of the velocity of the rightward or leftward travel of thepredetermined representative point or the first travel operation unitincreases.

The desired value of the turn angular velocity is preferably determinedsuch that the magnitude thereof is a predetermined upper limit value orless.

Further, the inverted pendulum type vehicle in accordance with thepresent invention may adopt the following mode. An inverted pendulumtype vehicle in accordance with the present invention has at least afirst travel operation unit capable of traveling on a floor surface, afirst actuator that drives the first travel operation unit, a base bodyto which the first travel operation unit and the first actuator areinstalled, and a rider mounting section attached to the base body suchthat the rider mounting section is tiltable relative to a verticaldirection, wherein the first travel operation unit is configured to becapable of traveling in all directions, including a longitudinaldirection and a lateral direction relative to a rider on the ridermounting section, by a driving force of the first actuator, the invertedpendulum type vehicle including:

a second travel operation unit, which is connected to the first traveloperation unit or the base body with an interval provided from the firsttravel operation unit in the longitudinal direction and which isconfigured to be capable of traveling in all directions on a floorsurface;

a second actuator which generates a driving force for causing the secondtravel operation unit to travel at least in the lateral direction; and

a control unit, which controls the first actuator and the secondactuator so as to cause the first travel operation unit and the secondtravel operation unit to carry out travel motions thereof according toat least the tilt of the rider mounting section,

wherein the control unit is configured to carry out turning controlprocessing for controlling the travel velocity of the first traveloperation unit and the travel velocity of the second travel operationunit in the lateral direction through the first actuator and the secondactuator, respectively, such that the travel velocity of the firsttravel operation unit and the travel velocity of the second traveloperation unit differ from each other so as to cause the invertedpendulum type vehicle to turn about the turn center on the rear side ofthe ground contact point of the first travel operation unit in asituation in which the rider on the rider mounting section has shiftedhis/her center of gravity to the right or left relatively with respectto the rider mounting section (a seventh aspect of the invention).

According to the seventh aspect of the invention, as with the firstaspect of the invention, the inverted pendulum type vehicle (hereinafterreferred to simply as “the vehicle” in some cases) is provided with, inaddition to the first travel operation unit and the first actuator, thesecond travel operation unit, which is disposed with the intervalprovided in the longitudinal direction relative to the first traveloperation unit and which is capable of traveling in all directions, anda second actuator, which generates the driving force for causing thesecond travel operation unit to travel in the lateral direction.

As has been described in relation to the first aspect of the invention,when the rider on the rider mounting section intends to turn the vehicle(including the changing of the direction), the rider normally attemptsto shift his/her center of gravity to the right or left relatively withrespect to the rider mounting section so as to generate a velocitycomponent of the vehicle in the rightward or leftward direction, therebytilting the rider mounting section. In this case, the rider has atendency to shift his/her center of gravity to the right or left,whichever direction he or she intends to turn the vehicle. Further, inthis case, since the rider mounting section has a tendency to tiltrightward or leftward, the control unit moves the first travel operationunit rightward or leftward to prevent the tilt of the rider mountingsection.

Thus, in the situation wherein the rider has shifted his/her center ofgravity to the right or left relatively with respect to the ridermounting section, it is very likely that the rider is trying to turn thevehicle to the vehicle's right or left.

Hence, according to the seventh aspect of the invention, the controlunit carries out the turning control processing for controlling thetravel velocity of the first travel operation unit and the travelvelocity of the second travel operation unit in the lateral directionthrough the first actuator and the second actuator, respectively, suchthat the travel velocity of the first travel operation unit and thetravel velocity of the second travel operation unit differ from eachother so as to cause the inverted pendulum type vehicle to turn aboutthe turn center on the rear side of the ground contact point of thefirst travel operation unit in a situation in which the rider on therider mounting section has shifted his/her center of gravity to theright or left relatively with respect to the rider mounting section.

This will cause the vehicle to turn due to the difference between thetravel velocity of the first travel operation unit and the travelvelocity of the second travel operation unit in the lateral direction.Further, in this case, the turn center of the vehicle is located on therear side of the ground contact point of the first travel operationunit. Hence, if the rider shifts his/her center of gravity to the leftrelative to the rider mounting section, then the vehicle is turned tothe left, i.e., turned in the counterclockwise direction. Further, ifthe rider shifts his/her center of gravity to the right relative to therider mounting section, then the vehicle is turned to the right, i.e.,turned in the clockwise direction.

Thus, the inverted pendulum type vehicle according to the seventh aspectof the invention enables the rider on the rider mounting section to turnthe vehicle in the direction that matches the direction (rightward orleftward) of the motion of his/her body simply by moving his/her body,i.e., tilting the rider mounting section to the right or left, so as tomove the first travel operation unit rightward or leftward.

Consequently, the inverted pendulum type vehicle according to theseventh aspect of the invention provides improved maneuverability of thevehicle, permitting easier turning of the vehicle.

In the seventh aspect of the invention, although the second traveloperation unit may be disposed in front of the first travel operationunit, the second travel operation unit is preferably disposed on therear side of the first travel operation unit (an eighth aspect of theinvention).

According to the eighth aspect of the invention, as with the secondaspect of the invention, the magnitude of the lateral travel velocity ofthe second travel operation unit when the vehicle is turned by theturning control processing can be reduced, as compared with the casewhere the second travel operation unit is disposed in front of the firsttravel operation unit. This makes it possible to restrain the occurrenceof the slip of the second travel operation unit and also to reduce thecapability required of the second actuator.

Further, in the seventh aspect or the eighth aspect of the invention, itis possible to control the travel velocities of the first traveloperation unit and the second travel operation unit in the lateraldirection such that the position of the turn center, i.e., the relativeposition with respect to the vehicle, is maintained at a fixed position.

However, the control unit is preferably configured to control, throughthe first actuator and the second actuator, the travel velocity of thefirst travel operation unit and the travel velocity of the second traveloperation unit in the lateral direction on the basis of a desired valueor an observed value of the travel velocity of the predeterminedrepresentative point, which has been set beforehand, or the first traveloperation unit in a forward direction such that the position of the turncenter in the longitudinal direction is moved toward the front on therear side of the rider on the rider mounting section as the magnitude ofthe desired value or the observed value of the travel velocity of thepredetermined representative point of the inverted pendulum type vehicleor the first travel operation unit in the forward direction increases inthe turning control processing (a ninth aspect of the invention).

According to the ninth aspect of the invention, as with the third aspectof the invention, the position of the turn center in the longitudinaldirection is shifted closer to a position immediately below the rider onthe rider mounting section as the magnitude of the desired value or theobserved value of the travel velocity of the predeterminedrepresentative point (the representative point of the vehicle) or thefirst travel operation unit in the forward direction increases when thevehicle is turned by the turning control processing. Hence, it becomeseasier to make the position of the rider (the position projected onto afloor surface) trace a desired path when the vehicle is turned.

This arrangement makes it easier for the rider to move his/her body tomake a desired turn while moving the vehicle forward.

Further, the inverted pendulum type vehicle in accordance with thepresent invention may adopt the following mode. An inverted pendulumtype vehicle in accordance with the present invention has at least afirst travel operation unit capable of traveling on a floor surface, afirst actuator that drives the first travel operation unit, a base bodyto which the first travel operation unit and the first actuator areinstalled, and a rider mounting section attached to the base body suchthat the rider mounting section is tiltable relative to a verticaldirection, wherein the first travel operation unit is configured to becapable of traveling in all directions, including a longitudinaldirection and a lateral direction relative to a rider on the ridermounting section, by a driving force of the first actuator, the invertedpendulum type vehicle including:

a second travel operation unit, which is connected to the first traveloperation unit or the base body with an interval provided from the firsttravel operation unit in the longitudinal direction and which isconfigured to be capable of traveling in all directions on a floorsurface;

a second actuator which generates a driving force for causing the secondtravel operation unit to travel at least in the lateral direction;

a control unit, which controls the first actuator and the secondactuator so as to cause the first travel operation unit and the secondtravel operation unit to carry out travel motions thereof according toat least the tilt of the rider mounting section; and a total center ofgravity offset estimating unit which estimates a lateral total center ofgravity offset amount, which is the amount of a lateral relativemovement of the total center of gravity of the rider and the invertedpendulum type vehicle with respect to the rider mounting section, thelateral total center of gravity offset amount being accrued due to therider on the rider mounting section having shifted his/her center ofgravity to the right or left relatively with respect to the ridermounting section,

wherein the control unit is configured to carry out turning controlprocessing for controlling the travel velocity of the first traveloperation unit and the travel velocity of the second travel operationunit in the lateral direction through the first actuator and the secondactuator, respectively, on the basis of a lateral total center ofgravity offset amount estimated by the total center of gravity offsetestimating unit so as to turn the inverted pendulum type vehicle aboutthe turn center on the rear side of the ground contact point of thefirst travel operation unit in a situation in which the rider on therider mounting section has shifted his/her center of gravity to theright or left relatively with respect to the rider mounting section (atenth aspect of the invention).

According to the tenth aspect of the invention, as with the seventhaspect of the invention, the inverted pendulum type vehicle (hereinafterreferred to simply as “the vehicle” in some cases) is provided with, inaddition to the first travel operation unit and the first actuator, thesecond travel operation unit, which is disposed with the intervalprovided in the longitudinal direction relative to the first traveloperation unit and which is capable of traveling in all directions, anda second actuator, which generates the driving force for causing thesecond travel operation unit to travel in the lateral direction.

As has been described in the seventh aspect of the invention, in thesituation wherein the rider has shifted his/her center of gravity to theright or left relatively with respect to the rider mounting section, itis very likely that the rider is trying to turn the vehicle to thevehicle's right or left.

Hence, according to the tenth aspect of the invention, the lateral totalcenter of gravity offset amount is estimated by the total center ofgravity offset estimating unit. Then, the control unit carries out theturning control processing for controlling the travel velocity of thefirst travel operation unit and the travel velocity of the second traveloperation unit in the lateral direction through the first actuator andthe second actuator, respectively, on the basis of the lateral totalcenter of gravity offset amount estimated by the total center of gravityoffset estimating unit so as to cause the inverted pendulum type vehicleto turn about the turn center on the rear side of the ground contactpoint of the first travel operation unit in a situation in which therider on the rider mounting section has shifted his/her center ofgravity to the right or left relatively with respect to the ridermounting section.

This will cause the vehicle to turn. Further, in this case, the turncenter of the vehicle is located on the rear side of the ground contactpoint of the first travel operation unit. Hence, if the rider shiftshis/her center of gravity to the left relative to the rider mountingsection, then the vehicle is turned to the left, i.e., turned in thecounterclockwise direction. Further, if the rider shifts his/her centerof gravity to the right relative to the rider mounting section, then thevehicle is turned to the right, i.e., turned in the clockwise direction.

Thus, as with the seventh aspect of the invention, the inverted pendulumtype vehicle according to the tenth aspect of the invention enables therider on the rider mounting section to turn the vehicle in the directionthat matches the direction (rightward or leftward) of the motion ofhis/her body simply by moving his/her body, i.e., tilting the ridermounting section to the right or left, so as to move the first traveloperation unit rightward or leftward.

Consequently, the inverted pendulum type vehicle according to the tenthaspect of the invention provides improved maneuverability of thevehicle, permitting easier turning of the vehicle.

In the tenth aspect of the invention, the control unit is preferablyconfigured to carry out the turning control processing in a situation,wherein the magnitude of the estimated value of the lateral total centerof gravity offset amount is a predetermined value or more, and tocontrol the first actuator and the second actuator such that the travelvelocity of the first travel operation unit and the travel velocity ofthe second travel operation unit in the lateral direction are the samewith each other in a situation wherein the magnitude of the estimatedvalue of the lateral total center of gravity offset amount is smallerthan the predetermined value (an eleventh aspect of the invention).

According to the eleventh aspect of the invention, in the situationwherein the magnitude of the estimated value of the lateral total centerof gravity offset amount is smaller than the predetermined value, thefirst actuator and the second actuator are controlled such that thetravel velocity of the first travel operation unit and the travelvelocity of the second travel operation unit in the lateral directionare the same with each other.

This arrangement makes it possible to prevent the vehicle from beingaccidentally turned due to an unintended reel of the body of the riderwhen the rider does not intend to turn the vehicle. In addition, atranslational travel of the vehicle in the lateral direction can bemade, as necessary.

Further, in the situation wherein the magnitude of the estimated valueof the lateral total center of gravity offset amount is thepredetermined value or more, the turning control processing is carriedout. This enables the rider to easily turn the vehicle simply byexplicitly moving his/her center of gravity rightward or leftward whenturning the vehicle.

The estimated value of the lateral total center of gravity offset amountcan be sequentially calculated by, for example, the operation shown inthe block diagram of FIG. 7, which will be discussed hereinafter.

To be more specific, the estimated value of the lateral total center ofgravity offset amount can be sequentially determined to converge to anactual value by multiplying the difference between a first estimatedvalue Vb_estm1_y and a second estimated value Vb_estm2_y of the lateraltravel velocity of the total center of gravity of the vehicle and therider (hereinafter referred to as “the vehicle system total center ofgravity” in some cases) by a gain of a predetermined value setbeforehand.

In this case, the first estimated value Vb_estm1_y is an estimated valueof the lateral travel velocity of the vehicle system total center ofgravity kinematically calculated according to expression (A) givenbelow. The second estimated value Vb_estm2_y is an estimated value ofthe travel velocity calculated by integrating a lateral travelacceleration DVb_estm_y of the vehicle system total center of gravitydynamically calculated according to expression (B) given below.

Vb_estm1_(—) y=Vw1_act_(—) y+h·ωb_act_(—) y  (A)

DVb_estm_(—) y=(θb_act_(—) y·(h−r)+Ofst_estm_(—)y(k−1))·(g/h)+Vb_estm1_(—) x·ωz_act  (B)

whereVw1_act_y: Observed value of the lateral travel velocity of the firsttravel operation unith: Value set beforehand as the height of the vehicle system total centerof gravity from a floor surfaceωb_act_y: Observed value of the angular velocity of a tilt about thelongitudinal axis of the rider mounting sectionθb_act_y: Observed value of a tilt angle (tilt angle relative to thevertical direction) about the longitudinal axis of the rider mountingsectionr: Height of a tilt center from a floor surface about the longitudinalaxis of the rider mounting sectionOfst_estm_y(k−1): Latest value of the estimated value of the lateraltotal center of gravity offset amount that has been calculatedg: Gravitational acceleration constantVb_estm1_x: Estimated value of the longitudinal travel velocity of thevehicle system total center of gravity calculated according toexpression (C) given below

Vb_estm1_(—) x=Vw1_act_(—) x+h·ωb_act_(—) x  (C)

Vw1_act_x: Observed value of the longitudinal travel velocity of thefirst travel operation unitωb_act_x: Observed value of the angular velocity of a tilt about thelateral axis of the rider mounting sectionωz_act: Angular velocity about a yaw axis of the vehicle

In the eleventh aspect of the invention, the control unit is preferablyconfigured to determine a desired value of a turn angular velocity ofthe inverted pendulum type vehicle on the basis of at least theestimated value of the lateral total center of gravity offset amount andto control the velocities of the travels of the first travel operationunit and the second travel operation unit in the lateral direction onthe basis of the desired value of the turn angular velocity through thefirst actuator and the second actuator, respectively, in the turningcontrol processing (a twelfth aspect of the invention).

According to the twelfth aspect of the invention, the desired value ofthe turn angular velocity of the inverted pendulum type vehicle isdetermined on the basis of at least the estimated value of the lateraltotal center of gravity offset amount in the turning control processing.This arrangement enables the rider to change the turning velocity of thevehicle to a desired turning velocity by adjusting the motion of his/herown body in the lateral direction.

In this case, for example, the desired value of the turn angularvelocity is preferably determined such that the magnitude of the desiredvalue of the turn angular velocity increases as the magnitude of theestimated value of the lateral total center of gravity offset amountincreases.

The desired value of the turn angular velocity is preferably determinedsuch that the magnitude thereof is a predetermined upper limit value orless.

In the tenth aspect to the twelfth aspect of the invention, although thesecond travel operation unit may be disposed in front of the firsttravel operation unit, the second travel operation unit is preferablydisposed on the rear side of the first travel operation unit (athirteenth aspect of the invention).

According to the thirteenth aspect of the invention, as with the secondaspect of the invention, the magnitude of the lateral travel velocity ofthe second travel operation unit when the vehicle is turned by theturning control processing can be reduced, as compared with the casewhere the second travel operation unit is disposed in front of the firsttravel operation unit. This makes it possible to restrain the occurrenceof the slip of the second travel operation unit and also to reduce thecapability required of the second actuator.

Further, in the tenth aspect to the thirteenth aspect of the invention,it is possible to control the travel velocities of the first traveloperation unit and the second travel operation unit in the lateraldirection such that the position of the turn center, i.e., the relativeposition with respect to the vehicle, is maintained at a fixed position.

However, the control unit is preferably configured to control, throughthe first actuator and the second actuator, the travel velocity of thefirst travel operation unit and the travel velocity of the second traveloperation unit, respectively, in the lateral direction on the basis of adesired value or an observed value of the travel velocity of thepredetermined representative point or the first travel operation unit ina forward direction such that the position of the turn center in thelongitudinal direction is moved toward the front on the rear side of therider on the rider mounting section as the magnitude of the desiredvalue or the observed value of the travel velocity of the predeterminedrepresentative point of the inverted pendulum type vehicle, which hasbeen set beforehand, or the first travel operation unit in the forwarddirection increases in the turning control processing (a fourteenthaspect of the invention).

According to the fourteenth aspect of the invention, as with the thirdaspect of the invention, the position of the turn center in thelongitudinal direction is shifted closer to a position immediately belowthe rider on the rider mounting section as the magnitude of the desiredvalue or the observed value of the travel velocity of the predeterminedrepresentative point (the representative point of the vehicle) or thefirst travel operation unit in the longitudinal direction increases whenthe vehicle is turned by the turning control processing. Hence, itbecomes easier to make the position of the rider (the position projectedonto a floor surface) trace a desired path when the vehicle is turned.

This arrangement makes it easier for the rider to move his/her body tomake a desired turn while moving the vehicle forward.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating the appearance of an invertedpendulum type vehicle according to a first embodiment of the presentinvention;

FIG. 2 is a side view of the inverted pendulum type vehicle according tothe first embodiment;

FIG. 3 is a block diagram illustrating the configuration for controllingthe inverted pendulum type vehicle according to the first embodiment;

FIG. 4 is a block diagram illustrating the processing by a first controlprocessor shown in FIG. 3;

FIG. 5 is a diagram illustrating an inverted pendulum model used for theprocessing by the first control processor shown in FIG. 3;

FIG. 6 is a block diagram illustrating behaviors related to the invertedpendulum model shown in FIG. 5;

FIG. 7 is a block diagram illustrating the processing by a center ofgravity offset estimator shown in FIG. 4;

FIG. 8 is a block diagram illustrating the processing by a secondcontrol processor shown in FIG. 3; and

FIG. 9A is a block diagram illustrating the processing by an essentialsection of a second control processor in a second embodiment of thepresent invention, and FIG. 9B is a block diagram illustrating theprocessing by an essential section of a second control processor in athird embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present invention will be described withreference to FIG. 1 to FIG. 8. As illustrated in FIG. 1 and FIG. 2, aninverted pendulum type vehicle 1 according to the present embodiment(hereinafter referred to simply as the vehicle 1 in some cases) has abase body 2, a first travel operation unit 3 and a second traveloperation unit 4, which are capable of traveling on a floor surface, anda rider mounting section 5 on which a rider mounts.

The first travel operation unit 3 includes a circular core member 6shown in FIG. 2 (hereinafter referred to as the annular core member 6)and a plurality of circular rollers 7 mounted on the annular core member6 such that the circular rollers 7 are arranged at equiangular intervalsin the circumferential direction (in the direction about the axialcenter) of the annular core member 6. Each of the rollers 7 isexternally inserted into the annular core member 6 with its rotationalaxial center directed toward the circumference of the annular coremember 6. Further, each of the rollers 7 is configured to be rotatableintegrally with the annular core member 6 about the axial center of theannular core member 6. In addition, each of the rollers 7 is configuredto be rotatable about the central axis of the cross-sectional plane ofthe annular core member 6 (the circumferential axis about the axialcenter of the annular core member 6).

The first travel operation unit 3 having the annular core member 6 andthe plurality of the rollers 7 comes in contact with a floor surfacethrough the intermediary of the rollers 7 (the rollers 7 positioned in alower portion of the annular core member 6), the axial center of theannular core member 6 being directed in parallel to the floor surface.In this ground contact state, the annular core member 6 is rotativelydriven about the axial center thereof so as to cause all the annularcore member 6 and the rollers 7 to circumrotate. This in turn causes thefirst travel operation unit 3 to travel on the floor surface in adirection orthogonal to the axial center of the annular core member 6.In the ground contact state, rotatively driving the rollers 7 abouttheir rotational axial centers causes the first travel operation unit 3to travel in the direction of the axial center of the annular coremember 6.

Further, rotatively driving the annular core member 6 and rotativelydriving the rollers 7 cause the first travel operation unit 3 to travelin a direction at an angle with respect to the direction orthogonal tothe axial center of the annular core member 6 and the direction of theaxial center of the annular core member 6.

Thus, the first travel operation unit 3 is capable of traveling on thefloor surface in all directions. In the following description, of thetraveling directions of the first travel operation unit 3, the directionorthogonal to the axial center of the annular core member 6 is definedas X-axis direction, the direction of the axial center of the annularcore member 6 is defined as Y-axis direction, and a vertical directionis defined as Z-axis direction, as illustrated in FIG. 1 and FIG. 2. Inaddition, a forward direction is defined as the positive direction ofthe X-axis, a left direction is defined as the positive direction of theY-axis, and an upper direction is defined as a positive direction of theZ-axis.

The first travel operation unit 3 is installed to the base body 2. Morespecifically, the base body 2 is provided, covering the first traveloperation unit 3 except for a lower portion thereof in contact with thefloor surface. Further, the base body 2 supports the annular core member6 of the first travel operation unit 3 such that the annular core member6 is rotatable about the axial center thereof.

In this case, the base body 2 uses the axial center of the annular coremember 6 of the first travel operation unit 3 as the supporting pointthereof and the base body 2 can be tilted about the axial center (aboutthe Y-axis). Further, the base body 2 is tiltable about the X-axisorthogonal to the axial center of the annular core member 6 by tiltingtogether with the first travel operation unit 3 relative to the floorsurface, the ground contact portion of the first travel operation unit 3being the supporting point. Thus, the base body 2 is tiltable about twoaxes relative to the vertical direction.

The base body 2 includes therein a first actuator 8, which generates adriving force for moving the first travel operation unit 3, asillustrated in FIG. 2. The first actuator 8 is constituted of anelectric motor 8 a serving as the actuator that rotatively drives theannular core member 6 and an electric motor 8 b serving as the actuatorthat rotatively drives the rollers 7. The electric motors 8 a and 8 bimpart rotative driving forces to the annular core member 6 and therollers 7 through the intermediary of a motive power transmittingmechanisms (not shown). The motive power transmitting mechanisms mayhave publicly known constructions.

The first travel operation unit 3 may have a construction different fromthe aforesaid construction. For example, the first travel operation unit3 and the driving system thereof may adopt the constructions proposed bythe applicant of the present application in PCT WO/2008/132778 or PCTWO/2008/132779.

Further, the rider mounting section 5 is installed to the base body 2.The rider mounting section 5 is formed of a seat, on which a rider sits,and fixed to the upper end portion of the base body 2. A rider can siton the rider mounting section 5, the longitudinal direction thereofbeing the X-axis direction and the lateral direction thereof being theY-axis direction. The rider mounting section 5 (the seat) is secured tothe base body 2, so that the rider mounting section 5 can be tiltedintegrally with the base body 2 relative to the vertical direction.

Further attached to the base body 2 are a pair of footrests 9 and 9, onwhich the rider sitting on the rider mounting section 5 places his/herfeet, and a pair of handles 10 and 10 held by the rider.

The footrests 9 and 9 are protrusively provided in lower portions ofboth sides of the base body 2. In FIG. 1 and FIG. 2, one (the right one)of the footrests 9 is not shown.

The handles 10 and 10 are formed of bar-like members disposed extendedlyin the X-axis direction (the longitudinal direction) on both sides ofthe rider mounting section 5. The handles 10 and 10 are respectivelyfixed to the base body 2 through rods 11 extended from the base body 2.Further, a joystick 12 serving as an operation device is attached to onehandle 10 (the right handle 10 in the drawing) of the pair of handles 10and 10.

The joystick 12 can be swung in the longitudinal direction (the X-axisdirection) and the lateral direction (the Y-axis direction). Thejoystick 12 outputs an operation signal indicative of the amount ofswing in the longitudinal direction (the X-axis direction) and thedirection of the swing (forward or backward) as a forward/backwardtravel command for moving the vehicle 1 forward or backward. Thejoystick 12 also outputs an operation signal indicative of the amount ofswing in the lateral direction (the Y-axis direction) and the directionof the swing (rightward or leftward) as a lateral travel command formoving the vehicle 1 in the lateral direction.

The second travel operation unit 4 in the present embodiment is formedof a so-called omniwheel. The omniwheel constituting the second traveloperation unit 4 has a publicly known structure, which includes a pairof coaxial annular core members (not shown) and a plurality ofbarrel-like rollers 13 rotatably and externally inserted in each of theannular core members with the rotational axial centers thereof orientedin the circumferential direction of the annular core member.

In this case, the second travel operation unit 4 is disposed at the rearof the first travel operation unit 3 with the axial centers of the pairof annular core members thereof oriented in the X-axis direction (thelongitudinal direction). Further, the second travel operation unit 4 isin contact with a floor surface through the rollers 13.

The roller 13 of one of the pair of annular core members and the roller13 of the other thereof are arranged such that the phases thereof areshifted in the peripheral directions of the annular core members. Therollers 13 are further configured such that either the roller 13 of oneof the pair of annular core members or the roller 13 of the otherthereof comes in contact with the floor surface when the pair of annularcore members rotates.

The second travel operation unit 4 constituted of the omniwheel isjoined to the base body 2. More specifically, the second traveloperation unit 4 is provided with a housing 14 that covers an upperportion of the omniwheel (all the pair of annular core members and theplurality of the rollers 13). The pair of annular core members of theomniwheel is rotatably supported by the housing 14 such that the pair ofannular core members is rotatable about the axial centers thereof.Further, an arm 15 extended from the housing 14 to the base body 2 isrotatably supported by the base body 2 such that the arm 15 is swingableabout the axial center of the annular core member 6 of the first traveloperation unit 3. Thus, the second travel operation unit 4 is joined tothe base body 2 through the arm 15.

Further, the second travel operation unit 4 is swingable, relative tothe base body 2, about the axial center of the annular core member 6 ofthe first travel operation unit 3 by the swing of the arm 15. Thisallows the rider mounting section 5 to tilt together with the base body2 about the Y-axis while maintaining both the first travel operationunit 3 and the second travel operation unit 4 to be in contact with theground.

Alternatively, the arm 15 may be rotatably supported by the axial centerportion of the annular core member 6 of the first travel operation unit3, and the second travel operation unit 4 may be joined to the firsttravel operation unit 3 through the arm 15.

The base body 2 is provided with a pair of stoppers 16 and 16 thatrestricts the swing range of the arm 15. Hence, the arm 15 is allowed toswing within the range defined by the stoppers 16 and 16. This restrictsthe swing range of the second travel operation unit 4 about the axialcenter of the annular core member 6 of the first travel operation unit 3and consequently the range of tilt of the base body 2 and the ridermounting section 5 about the X-axis. As a result, the base body 2 andthe rider mounting section 5 are prevented from excessively tiltingtoward the rear side of the rider.

The second travel operation unit 4 may be urged by a spring so as to bepressed against the floor surface.

As described above, the second travel operation unit 4 is capable oftraveling on the floor surface in all directions, including the X-axisdirection and the Y-axis direction, as with the first travel operationunit 3, by rotating one or both of the pair of annular core members andthe rollers 13. More specifically, the rotation of the annular coremembers enables the second travel operation unit 4 to travel in theY-axis direction, i.e., the lateral direction. Further, the rotation ofthe rollers 13 enables the second travel operation unit 4 to travel inthe X-axis direction, i.e., the longitudinal direction.

An electric motor 17 serving as the second actuator, which drives thesecond travel operation unit 4, is attached to the housing 14 of thesecond travel operation unit 4. The electric motor 17 is joined to thepair of annular core members so as to rotatively drive the pair ofannular core members of the second travel operation unit 4.

Thus, according to the present embodiment, the travel of the secondtravel operation unit 4 in the X-axis direction is adapted to passivelyfollow the travel of the first travel operation unit 3 in the X-axisdirection. Further, the travel of the second travel operation unit 4 inthe Y-axis direction is implemented by rotatively driving the pair ofannular core members of the second travel operation unit 4 by theelectric motor 17.

Supplementarily, the second travel operation unit 4 may have the sameconstruction as that of the first travel operation unit 3.

The above has described the mechanical configuration of the vehicle 1according to the present embodiment.

Although not shown in FIG. 1 and FIG. 2, in order to control theoperation of the vehicle 1, i.e., to control the operations of the firsttravel operation unit 3 and the second travel operation unit 4, the basebody 2 of the vehicle 1 in the present embodiment incorporates acontroller 21 constituted of an electronic circuit unit, which includesa CPU, a RAM, a ROM and the like, a tilt sensor 22 for measuring thetilt angle of the rider mounting section 5 (the tilt angle of the basebody 2) relative to the vertical direction, and a yaw rate sensor 23 formeasuring the angular velocity of the vehicle 1 about the yaw axis, asillustrated in FIG. 3.

The controller 21 corresponds to the controlling means in the presentinvention. The controller 21 receives the outputs of the joystick 12 anddetection signals of the tilt sensor 22 and the yaw rate sensor 23.

The controller 21 may alternatively be constituted of a plurality ofelectronic circuit units adapted to communicate with each other.

The tilt sensor 22 is constituted of, for example, an accelerationsensor and an angular velocity sensor, such as a gyro sensor. Thecontroller 21 uses a publicly known method to acquire the measurementvalue of the tilt angle of the rider mounting section 5, i.e., the tiltangle of the base body 2, from the detection signals of the accelerationsensor and the angular velocity sensor. As the method, the one proposedby the applicant of the present application in, for example, JapanesePatent No. 4181113 may be used.

More specifically, the tilt angle of the rider mounting section 5 (orthe tilt angle of the base body 2) in the present embodiment is the tiltangle (a set of a tilt angle in the direction about the X-axis and atilt angle in the direction about the Y-axis), which uses, as itsreference (zero), the posture of the rider mounting section 5 (or thebase body 2) in a state wherein the center of gravity of the combinationof the vehicle 1 and the rider mounted on the rider mounting section 5in a predetermined posture (standard posture) is positioned right abovethe ground contact portion of the first travel operation unit 3 (upwardin the vertical direction).

The yaw rate sensor 23 is composed of an angular velocity sensor, suchas a gyro sensor. Based on a detection signal of the yaw rate sensor 23,the controller 21 acquires the measurement value of the angular velocityof the vehicle 1 about the yaw axis.

To provide a function implemented by an installed program or the like (afunction implemented by software) or a function implemented by hardwarein addition to the function for acquiring the measurement values asdescribed above, the controller 21 further includes a first controlprocessor 24, which controls the electric motors 8 a and 8 bconstituting the first actuator 8 thereby to control the travelingmotion of the first travel operation unit 3, and a second controlprocessor 25, which controls the electric motor 17 serving as the secondactuator thereby to control the traveling motion of the second traveloperation unit 4.

The first control processor 24 carries out the arithmetic processing,which will be discussed hereinafter, to sequentially calculate a firstdesired velocity, which is the desired value of the travel velocity(more specifically, the set of a translational velocity in the X-axisdirection and a translational velocity in the Y-axis direction) of thefirst travel operation unit 3. Then, the first control processor 24controls the rotational speed of each of the electric motors 8 a and 8 bthereby to match the actual travel velocity of the first traveloperation unit 3 to the first desired velocity.

In this case, the relationship between the rotational speed of each ofthe electric motors 8 a and 8 b and the actual travel velocity of thefirst travel operation unit 3 is established beforehand. Hence, thedesired value of the rotational speed of each of the electric motors 8 aand 8 b is specified on the basis of the first desired velocity of thefirst travel operation unit 3. Then, the rotational speeds of theelectric motors 8 a and 8 b are feedback-controlled to the desiredvalues specified on the basis of the first desired velocity, therebycontrolling the actual travel velocity of the first travel operationunit 3 to the first desired velocity.

Further, the second control processor 25 carries out the arithmeticprocessing, which will be discussed hereinafter, to sequentiallycalculate a second desired velocity, which is the desired value of thetravel velocity (more specifically, the translational velocity in theY-axis direction) of the second travel operation unit 4. Then, thesecond control processor 25 controls the rotational speed of theelectric motor 17 thereby to match the actual travel velocity of thesecond travel operation unit 4 in the Y-axis direction to the seconddesired velocity.

In this case, the relationship between the rotational speed of theelectric motor 17 and the actual travel velocity of the second traveloperation unit 4 in the Y-axis direction is established beforehand, aswith the case of the first travel operation unit 3. Hence, the desiredvalue of the rotational speed of the electric motor 17 is specified onthe basis of the second desired velocity of the second travel operationunit 4. Then, the rotational speed of the electric motor 17 isfeedback-controlled to the desired values specified on the basis of thesecond desired velocity, thereby controlling the actual travel velocityof the second travel operation unit 4 in the Y-axis direction to thesecond desired velocity.

Supplementarily, according to the present embodiment, the travel of thesecond travel operation unit 4 in the X-axis direction is passivelyimplemented by following the travel of the first travel operation unit 3in the X-axis direction. Hence, there is no need to set the desiredvalue of the travel velocity of the second travel operation unit 4 inthe X-axis direction.

The processing by the first control processor 24 and the second controlprocessor 25 will now be described in further detail. First, theprocessing by the first control processor 24 will be described withreference to FIG. 4 to FIG. 7.

As illustrated in FIG. 4, the first control processor 24 has, as majorfunctional units thereof, an operation command converter 31, whichconverts commands (the turning command and the forward/backward command)received from the joystick 12 into velocity commands in the X-axisdirection (the longitudinal direction) and the Y-axis direction (thelateral direction) of the vehicle 1, a center of gravity desiredvelocity determiner 32, which determines the desired velocity of thetotal center of gravity of the combination of the vehicle 1 and therider on the rider mounting section 5 (hereinafter referred to as thevehicle system total center of gravity), a center of gravity velocityestimator 33 which estimates the velocity of the vehicle system totalcenter of gravity, and a posture control arithmetic unit 34 whichdetermines the desired value of the travel velocity of the first traveloperation unit 3 to control the posture of the rider mounting section 5,i.e., the posture of the base body 2, while making the estimatedvelocity of the vehicle system total center of gravity follow thedesired velocity. The first control processor 24 carries out theprocessing by the aforesaid functional units at a predeterminedarithmetic processing cycle of the controller 21.

In the present embodiment, the vehicle system total center of gravityhas a meaning as an example of the representative point of the vehicle1. Accordingly, the velocity of the vehicle system total center ofgravity has a meaning as the travel velocity of the representative pointof the vehicle 1.

Before specifically describing the processing carried out by each of thefunctional units of the first control processor 24, the basic matters ofthe processing will be described. The dynamic behavior of the vehiclesystem total center of gravity (more specifically, the behavior observedfrom the Y-axis direction and the behavior observed from the X-axisdirection) is approximately expressed by an inverted pendulum modelshown in FIG. 5. The algorithm of the processing by the first controlprocessor 24 is created on the basis of the behavior.

In the following description and FIG. 5, a suffix “_x” means a referencecode of a variable or the like observed from the Y-axis direction, whilea suffix “_y” means a reference code of a variable or the like observedfrom the X-axis direction. Further, in FIG. 5, the reference codes ofthe variables observed from the Y-axis direction are not parenthesized,while the reference codes of the variables observed from the X-axisdirection are parenthesized in order to illustrate both an invertedpendulum model observed from the Y-axis direction and an invertedpendulum model observed from the X-axis direction.

The inverted pendulum model expressing the behavior of the vehiclesystem total center of gravity observed from the Y-axis direction has avirtual wheel 61 _(—) x which has a rotational axial center parallel tothe Y-axis direction and which is circumrotatable on a floor surface(hereinafter referred to as “the virtual wheel 61 _(—) x”), a rod 62_(—) x which is extended from the rotational center of the virtual wheel61 _(—) x and which is swingable about the rotational axis of thevirtual wheel 61 _(—) x (in the direction about the Y-axis direction),and a mass point Ga_x connected to a reference portion Ps_x, which isthe distal end portion (upper end portion) of the rod 62 _(—) x.

In the inverted pendulum model, it is assumed that the movement of themass point Ga_x corresponds to the movement of the vehicle system totalcenter of gravity observed from the Y-axis direction, and a tilt angleθb_x (the angle of a tilt in the direction about the Y-axis) of the rod62 _(—) x relative to the vertical direction agrees with the angle of atilt of the rider mounting section 5 (or the base body 2) in thedirection about the Y-axis. Further, the translational movement of thefirst travel operation unit 3 in the X-axis direction corresponds to thetranslational movement in the X-axis direction by the circumrotation ofthe virtual wheel 61 _(—) x.

Further, a radius r_x of the virtual wheel 61 _(—) x and a height h_x ofeach of the reference portion Ps_x and the mass point Ga_x from thefloor surface are set to predetermined values (fixed values) setbeforehand. The radius r_x corresponds, in other words, to the height ofthe center of the tilt of the rider mounting section 5 (or the base body2) in the direction about the Y-axis from a floor surface. In thepresent invention, the r_x corresponds to the distance between thecentral axis of the annular core member 6 of the first travel operationunit 3 and the ground contact surface.

Similarly, the inverted pendulum model expressing the behavior of thevehicle system total center of gravity observed from the X-axisdirection has a virtual wheel 61 _(—) y which has a rotational axialcenter parallel to the X-axis direction and which is circumrotatable onthe floor surface (hereinafter referred to as “the virtual wheel 61 _(—)y”), a rod 62 _(—) y which is extended from the rotational center of thevirtual wheel 61 _(—) y and which is swingable about the rotational axisof the virtual wheel 61 _(—) y (in the direction about the X-axisdirection), and a mass point Ga_y connected to a reference portion Ps_y,which is the distal end portion (upper end portion) of the rod 62 _(—)y.

In the inverted pendulum model, it is assumed that the movement of themass point Ga_y corresponds to the movement of the vehicle system totalcenter of gravity observed from the X-axis direction. Further, a tiltangle θb_y (the angle of a tilt in the direction about the X-axis) ofthe rod 62 _(—) y relative to the vertical direction agrees with theangle of a tilt of the rider mounting section 5 (or the base body 2) inthe direction about the X-axis. Further, the translational movement ofthe first travel operation unit 3 in the Y-axis direction corresponds tothe translational movement in the Y-axis direction by the circumrotationof the virtual wheel 61 _(—) y.

Further, a radius r_y of the virtual wheel 61 _(—) y and a height h_y ofeach of the reference portion Ps_y and the mass point Ga_y from thefloor surface are set to predetermined values (fixed values) setbeforehand. The radius r_y corresponds, in other words, to the height ofthe center of the tilt of the rider mounting section 5 (or the base body2) in the direction about the X-axis from the floor surface. In thepresent invention, the r_y corresponds to the radius of each of therollers 7 of the first travel operation unit 3. Further, the height h_yof each of the reference portion Ps_y and the mass point Ga_y from thefloor surface observed in the X-axis direction is the same as the heighth_x of each of the reference portion Ps_x and the mass point Ga_x fromthe floor surface observed in the Y-axis direction. Hereinafter,therefore, h_x=h_y=h will apply.

The positional relationship between the reference portion Ps_x and themass point Ga_x observed from the Y-axis direction will besupplementarily described. The position of the reference portion Ps_xcorresponds to the position of the vehicle system total center ofgravity in the case where it is assumed that the rider mounting(sitting) on the rider mounting section 5 is motionless relative to therider mounting section 5. In this case, therefore, the position of themass point Ga_x agrees with the position of the reference portion Ps_x.The same applies to the positional relationship between the referenceportion Ps_y and the mass point Ga_y observed from the X-axis direction.

In practice, however, when the rider on the rider mounting section 5moves his/her upper body or the like relative to the rider mountingsection 5 (or the base body 2), the positions of the actual vehiclesystem total center of gravity in the X-axis direction and the Y-axisdirection will usually shift from the positions of the referenceportions Ps_x and Ps_y, respectively, in the horizontal direction. Forthis reason, the positions of the mass points Ga_x and Ga_y, which areshown in FIG. 5, are shifted from the positions of the referenceportions Ps_x and Ps_y, respectively.

The behavior of the vehicle system total center of gravity representedby the inverted pendulum model described above is denoted by thefollowing expressions (1a), (1b), (2a) and (2b). In this case,expressions (1a) and (1b) denote the behaviors observed in the Y-axisdirection, while expressions (2a) and (2b) denote the behaviors observedin the X-axis direction.

Vb _(—) x=Vw1_(—) x+h·ωb _(—) x  (1a)

dVb _(—) x/dt=(g/h)·(θb _(—) x·(h−r _(—) x)+Ofst_(—) x)+ωz·Vb _(—)y  (1b)

Vb _(—) y=Vw1_(—) y+h·ωb _(—) y  (2a)

dVb _(—) y/dt=(g/h)·(θb _(—) y·(h−r _(—) y)+Ofst_(—) y)−ωz·Vb _(—)x  (2b)

where Vb_x denotes the velocity of the vehicle system total center ofgravity in the X-axis direction (the translational velocity); Vw1_xdenotes the moving velocity (the translational velocity) of the virtualwheel 61 _(—) x in the X-axis direction; θb_x denotes the tilt angle ofthe rider mounting section 5 (or the base body 2) in the direction aboutthe Y-axis; ωb_x denotes the temporal change rate of θb_x (=dθb_x/dt);Ofst_x denotes the amount of a shift of the position of the vehiclesystem total center of gravity in the X-axis direction (the position ofthe mass point Ga_x in the X-axis direction) from the position of thereference portion Ps_x in the X-axis direction; Vb_y denotes thevelocity of the vehicle system total center of gravity in the Y-axisdirection (the translational velocity); Vw1_y denotes the movingvelocity (the translational velocity) of the virtual wheel 61 _(—) y inthe Y-axis direction; θb_y denotes the tilt angle of the rider mountingsection 5 (or the base body 2) in the direction about the X-axis; ωb_ydenotes the temporal change rate of θb_y (=dθb_y/dt); and Ofst_y denotesthe amount of shift of the position of the vehicle system total centerof gravity in the Y-axis direction (the position of the mass point Ga_yin the Y-axis direction) from the position of the reference portion Ps_yin the Y-axis direction. Further, ωz denotes a yaw rate (the angularvelocity in the direction about the yaw axis) when the vehicle 1 turns,and g denotes a gravitational acceleration constant. The positivedirection of θb_x and ωb_x is the direction in which the vehicle systemtotal center of gravity tilts in the positive direction of the X-axis(forward), while the positive direction of θb_y and ωb_y is thedirection in which the vehicle system total center of gravity tilts inthe positive direction of the Y-axis (leftward). Further, the positivedirection of ωz is the counterclockwise direction as the vehicle 1 isobserved from above.

Vb_x and Vb_y coincide with the travel velocity of the reference portionPs_x in the X-axis direction and the travel velocity of the referenceportion Ps_y in the Y-axis direction, respectively.

The second term of the right side of expression (1a), namely, (=h·ωb_x),denotes the translational velocity component of the reference portionPs_x in the X-axis direction generated by a tilt of the rider mountingsection 5 in the direction about the Y-axis. The second term of theright side of expression (2a), namely, (=h·ωb_y), denotes thetranslational velocity component of the reference portion Ps_y in theY-axis direction generated by a tilt of the rider mounting section 5 inthe direction about the X-axis.

Supplementarily, Vw1_x in expression (1a) specifically denotes arelative circumferential velocity of the virtual wheel 61 _(—) x withrespect to the rod 62 _(—) x (in other words, with respect to the ridermounting section 5 or the base body 2). Hence, Vw1_x includes a velocitycomponent (=r_x·ωb_x), which is generated when the rod 62 _(—) x tilts,in addition to the moving velocity of the ground contact point of thevirtual wheel 61 _(—) x in the X-axis direction relative to the floorsurface, i.e., the moving velocity of the ground contact point of thefirst travel operation unit 3 in the X-axis direction relative to thefloor surface. The same applies to Vw1_y in expression (1b).

Further, the first term of the right side of expression (1b) denotes anacceleration component in the X-axis direction generated at the vehiclesystem total center of gravity by a component in the X-axis direction(F_x in FIG. 5) of a floor reaction force (F in FIG. 5) acting on theground contact portion of the virtual wheel 61 _(—) x according to theamount of shift (=θb_x·(h−r_x)+Ofst_x) of the position of the vehiclesystem total center of gravity in the X-axis direction (the position ofthe mass point Ga_x in the X-axis direction) from the vertical upperposition of the ground contact portion of the virtual wheel 61 _(—) x(the ground contact portion of the first travel operation unit 3observed from the Y-axis direction). The second term of the right sideof expression (1b) denotes the acceleration component in the X-axisdirection generated by a centrifugal force acting on the vehicle 1 atthe time of turning at the yaw rate of ωz.

Similarly, the first term of the right side of expression (2b) denotesan acceleration component in the Y-axis direction generated at thevehicle system total center of gravity by a component in the Y-axisdirection (F_y in FIG. 5) of a floor reaction force (F in FIG. 5) actingon the ground contact portion of the virtual wheel 61 _(—) y accordingto the amount of deviation (=θb_y·(h−r_y)+Ofst_y) of the position of thevehicle system total center of gravity in the Y-axis direction (theposition of the mass point Ga_y in the Y-axis direction) from thevertical upper position of the ground contact portion of the virtualwheel 61 _(—) y (the ground contact portion of the first traveloperation unit 3 observed from the X-axis direction). The second term ofthe right side of expression (2b) denotes the acceleration component inthe Y-axis direction generated by a centrifugal force acting on thevehicle 1 at the time of turning at the yaw rate of ωz.

The behaviors (the behaviors observed in the X-axis direction)represented by expressions (1a) and (1b) described above are illustratedby the block diagram of FIG. 6. In the diagram, 1/s denotes integrationoperation.

Further, the processing by an arithmetic unit indicated by referencecharacter A in FIG. 6 corresponds to the relational expression ofexpression (1a), while the processing by an arithmetic unit indicated byreference character B corresponds to the relational expression ofexpression (1b).

In FIG. 6, h·θb_x approximately coincides with Diff_x shown in FIG. 5.

Meanwhile, the block diagram representing the behaviors indicated byexpressions (2a) and (2b), i.e., the behaviors observed in the Y-axisdirection, is obtained by replacing the suffix “_x” in FIG. 6 by “_y”and by replacing the sign “+” of the acceleration component (theacceleration component generated by the centrifugal force) at the lowerside in the drawing, which is one of the inputs to an adder denoted byreference character C, by “−.”

According to the present embodiment, the algorithm of the processing bythe first control processor 24 is created on the basis of the behaviormodel (inverted pendulum model) of the vehicle system total center ofgravity that considers the centrifugal force and the amount of the shiftof the vehicle system total center of gravity from the referenceportions Ps_x and Ps_y, as described above.

Based on the above, the processing by the first control processor 24will be specifically described. In the following description, the set ofthe value of a variable related to the behavior observed from the Y-axisdirection and the value of a variable related to the behavior observedfrom the X-axis direction will be denoted by adding a suffix “_xy” insome cases.

Referring to FIG. 4, the first control processor 24 first carries outthe processing by the operation command converter 31 and the processingby the center of gravity velocity estimator 33 at each arithmeticprocessing cycle of the controller 21.

The operation command converter 31 determines a basic velocity commandVjs_xy, which is the basic command value of the travel velocity (thetranslational velocity) of the first travel operation unit 3 on thebasis of the forward/backward command (the operation signal indicativeof the amount of swing of the joystick 12 in the X-axis direction andthe direction of the swing) or the lateral travel command (the operationsignal indicative of the amount of swing of the joystick 12 in theY-axis direction and the direction of the swing) received from thejoystick 12.

In this case, of the aforesaid basic velocity command Vjs_xy, the basicvelocity command Vjs_x in the X-axis direction is determined accordingto the forward/backward command. More specifically, if the amount of theswing of the joystick 12 indicated by the forward/backward command isthe amount of a forward swing, then the basic velocity command in theX-axis direction Vjs_x will be a velocity command for a forward movementdirection of the vehicle 1. If the amount of swing of the joystick 12 isthe amount of a backward swing, then the basic velocity command in theX-axis direction Vjs_x will be a velocity command for a backwardmovement direction of the vehicle 1. In this case, the magnitude of thebasic velocity command in the X-axis direction Vjs_x is determined suchthat it increases to a predetermined upper limit value or less as themagnitude of the amount of swing of the joystick 12 in the forward orthe backward direction increases.

A predetermined range in which the amount of the forward or backwardswing of the joystick 12 is sufficiently small may be defined as a deadzone, and the basic velocity command in the X-axis direction Vjs_x maybe set to zero for a swing amount in the dead zone.

Of the basic velocity commands Vjs_xy, the basic velocity command in theY-axis direction Vjs_y is determined according to the lateral travelcommand. More specifically, if the swing amount of the joystick 12indicated by the lateral travel command is a rightward swing amount,then the basic velocity command in the Y-axis direction Vjs_y is definedas the rightward velocity command for the vehicle 1. If the swing amountof the joystick 12 is a leftward swing amount, then the basic velocitycommand in the Y-axis direction Vjs_y is defined as the leftwardvelocity command for the vehicle 1. In this case, the magnitude of thebasic velocity command in the Y-axis direction Vjs_y is determined suchthat it increases to a predetermined upper limit value or less as therightward or leftward swing amount of the joystick 12 increases.

Regarding the magnitude of the basic velocity command Vjs_y, apredetermined range in which the amount of the rightward or leftwardswing of the joystick 12 is sufficiently small may be defined as a deadzone, and the basic velocity command in the Y-axis direction Vjs_y maybe set to zero for a swing amount in the dead zone.

If the joystick 12 is operated in both the longitudinal direction(X-axis direction) and the Y-axis direction (the lateral direction),then the magnitude of the basic velocity command in the Y-axis directionVjs_y may be set so as to change according to the swing amount of thejoystick 12 in the longitudinal direction or the basic velocity commandin the X-axis direction Vjs_x.

The center of gravity velocity estimator 33 calculates an estimatedvalue of the velocity of the vehicle system total center of gravityVb_estm1_xy according to the geometric (kinematic) relationshipexpressions given by the aforesaid expressions (1a) and (2a) in theinverted pendulum model.

More specifically, as illustrated by the block diagram in FIG. 4, thecenter of gravity velocity estimator 33 adds up the value of an actualtranslational velocity Vw1_act_xy of the first travel operation unit 3and the value, which is obtained by multiplying an actual temporalchange rate (tilt angular velocity) ωb_act_xy of a tilt angle θb_xy ofthe rider mounting section 5 by a height h of the vehicle system totalcenter of gravity to calculate the estimated value of the velocity ofthe vehicle system total center of gravity Vb_estm1_xy.

More specifically, the estimated value of the velocity in the X-axisdirection Vb_estm1_x of the vehicle system total center of gravity andthe estimated value of the velocity in the Y-axis direction Vb_estm1_ythereof are calculated according to the following expressions (3a) and(3b).

Vb_estm1_(—) x=Vw1_act_(—) x+h·ωb_act_(—) x  (3a)

Vb_estm1_(—) y=Vw1_act_(—) y+h·ωb_act_(—) y  (3b)

However, the temporal change rate of the offset amount Ofst_xy of theposition of the vehicle system total center of gravity from the positionof the reference portion Ps_xy (hereinafter referred to as the center ofgravity offset amount Ofst_xy) is set to be sufficiently smaller thanVb_estm1_xy so as to be ignorable.

In this case, according to the present embodiment, desired values of thetravel velocity Vw1_cmd_x and Vw1_cmd_y (previous values) of the firsttravel operation unit 3 determined by the posture control arithmeticunit 34 at the previous arithmetic processing cycle are used as thevalues of Vw1_act_x and Vw1_act_y in the above calculation.

Alternatively, however, the rotational speeds of the electric motors 8 aand 8 b, for example, may be detected by a rotational velocity sensor,such as a rotary encoder. Then, the latest values of Vw1_act_x andVw1_act_y (i.e., the latest values of the measurement values ofVw1_act_x and Vw1_act_y) estimated from the detection values may be usedfor the calculation of expressions (3a) and (3b).

Further, according to the present embodiment, the latest values of thetemporal change rates of the measurement values of the tilt angle θb ofthe rider mounting section 5 based on a detection signal of the tiltsensor 22 (i.e., the latest values of the measurement values of ωb_act_xand ωb_act_y) are used as the values of ωb_act_x and ωb_act_y.

After carrying out the processing by the operation command converter 31and the center of gravity velocity estimator 33 as described above, thefirst control processor 24 carries out the processing by a center ofgravity offset estimator 35 a illustrated in FIG. 4. Thus, the firstcontrol processor 24 determines a center of gravity offset amountestimated value Ofst_estm_xy, which is the estimated value of the centerof gravity offset amount Ofst_xy.

The processing by the center of gravity offset estimator 35 a is theprocessing indicated by the block diagram of FIG. 7. FIG. 7representatively illustrates the processing for determining theestimated value of the center of gravity offset amount in the X-axisdirection Ofst_estm_x of the estimated value of the center of gravityoffset amount Ofst_estm_xy.

The processing in FIG. 8 will be specifically described. The center ofgravity estimator 35 a carries out the arithmetic processing of theright side of the aforesaid expression (1b) by an arithmetic unit 35 a 1by using a measurement value (a latest value) of an actual tilt angle inthe direction about the Y-axis θb_act_x of the rider mounting section 5obtained from a detection signal of the tilt sensor 22, a measurementvalue (a latest value) of an actual yaw rate ωz_act of the vehicle 1obtained from a detection signal of the yaw rate sensor 23, a firstestimated value (a latest value) of the velocity of the vehicle systemtotal center of gravity in the Y-axis direction Vb_estm1_y calculated bythe center of gravity velocity estimator 33, and the estimated value ofthe center of gravity offset amount in the X-axis direction Ofst_estm_x(a previous value) determined at the previous arithmetic processingcycle. Thus, the center of gravity offset estimator 35 a calculates anestimated value of the translational acceleration of the vehicle systemtotal center of gravity in the X-axis direction DVb_estm_x.

The center of gravity offset estimator 35 a further carries out theprocessing for integrating the estimated value of the translationalacceleration in the X-axis direction DVb_estm_x of the vehicle systemtotal center of gravity by an arithmetic unit 35 a 2. Thus, the centerof gravity offset estimator 35 a calculates a second estimated value ofthe velocity of the vehicle system total center of gravity in the X-axisdirection Vb_estm2_x.

Subsequently, the center of gravity offset estimator 35 a carries outthe processing for calculating the difference between the secondestimated value of the velocity of the vehicle system total center ofgravity in the X-axis direction Vb_estm2_x (a latest value) and thefirst estimated value Vb_estm1_x (a latest value) thereof by anarithmetic unit 35 a 3.

Then, the center of gravity offset estimator 35 a further carries outthe processing for multiplying the difference by a gain (−Kp) of apredetermined value by an arithmetic unit 35 a 4. Thus, the center ofgravity offset estimator 35 a determines the latest value of theestimated value of the center of gravity offset amount in the X-axisdirection Ofst_estm_x.

The processing for determining the estimated value of the center ofgravity offset amount in the Y-axis direction Ofst_estm_y is alsocarried out in the same manner described above. More specifically, theblock diagram illustrating the determination processing can be obtainedby replacing the suffix “_x” in FIG. 7 by “_y” and by replacing the sign“+” of the acceleration component (an acceleration component generatedby a centrifugal force) at right in the drawing, which is one of theinputs to an adder 35 a 5, by “−”.

The estimated value of the center of gravity offset amount Ofst_estm_xyis determined while being updated by the aforesaid processing carriedout by the center of gravity offset estimator 35 a. This makes itpossible to converge Ofst_estm_xy to an actual value.

The first control processor 24 then carries out the processing by acenter of gravity offset influence amount calculator 35 b shown in FIG.4 to calculate a center of gravity offset influence amount Vofs_xy.

The center of gravity offset influence amount Vofs_xy indicates thedeviation of an actual center of gravity velocity from a desiredvelocity of the vehicle system total center of gravity in the case wherethe feedback control is conducted in the posture control arithmetic unit34, which will be discussed hereinafter, without considering thedeviation of the position of the vehicle system total center of gravityfrom the position of the reference portion Ps_xy in the invertedpendulum mode.

To be specific, the center of gravity offset influence amount calculator35 b multiplies each component of a newly determined estimated value ofthe center of gravity offset amount Ofst_estm_xy by a value denoted by(Kth_xy/(h_r_xy))/Kvb_xy, thereby calculating the center of gravityoffset influence amount Vofs_xy.

Kth_xy denotes a gain value for determining a manipulated variablecomponent which functions to bring the tilt angle of the rider mountingsection 5 close to zero, i.e., to a desired tilt angle, in theprocessing by the posture control arithmetic unit 34, which will behereinafter discussed. Further, Kvb_xy denotes a gain value fordetermining a manipulated variable component which functions to bringthe difference between a desired velocity of the vehicle system totalcenter of gravity Vb_cmd_xy and the first estimated value of thevelocity of the vehicle system total center of gravity Vb_estm1_xy closeto zero in the processing carried out by the posture control arithmeticunit 34, which will be hereinafter discussed.

The first control processor 24 then carries out the processing by thecenter of gravity desired velocity determiner 32 shown in FIG. 4. Thus,the first control processor 24 calculates a restricted center of gravitydesired velocity Vb_cmd_xy on the basis of the basic velocity commandVjs_xy determined by the operation command converter 31 and the centerof gravity offset influence amount Vofs_xy determined by the center ofgravity offset influence amount calculator 35 b.

The center of gravity desired velocity determiner 32 first carries outthe processing through a processor 32 c shown in FIG. 4. The processor32 c carries out dead-zone processing and limiting related to the valueof the center of gravity offset influence amount Vofs_xy thereby todetermine a desired center of gravity velocity additive amountVb_cmd_by_ofs_xy as a component based on the center of gravity offset ofa desired value of the vehicle system total center of gravity.

More specifically, according to the present embodiment, if the magnitudeof the center of gravity offset influence amount in the X-axis directionVofs_x is a value within a dead zone, which is a predetermined range inthe vicinity of zero, i.e., a value that is relatively close to zero,then the center of gravity desired velocity determiner 32 sets thedesired center of gravity velocity additive amount in the X-axisdirection Vb_cmd_by_ofs_x to zero.

Further, if the magnitude of the center of gravity offset influenceamount in the X-axis direction Vofs_x is a value that deviates from thedead zone, then the center of gravity desired velocity determiner 32determines the desired center of gravity velocity additive amount in theX-axis direction Vb_cmd_by_ofs_x such that the polarity thereof is thesame as Vofs_x and the magnitude thereof increases as the magnitude ofVofs_x increases. However, the value of the desired center of gravityvelocity additive amount Vb_cmd_by_ofs_x is restricted to the range froma predetermined upper limit value (>0) to a predetermined lower limitvalue (≦0).

The processing for determining the desired center of gravity velocityadditive amount in the Y-axis direction Vb_cmd_by_ofs_y is the same asthe processing described above.

Subsequently, the center of gravity desired velocity determiner 32carries out, by a processor 32 d shown in FIG. 4, the processing fordetermining a desired velocity V1_xy obtained by adding each componentof the desired center of gravity velocity additive amountVb_cmd_by_ofs_xy to each component of the basic velocity command Vjs_xydetermined by the operation command converter 31. More specifically, thecenter of gravity desired velocity determiner 32 determines V1_xy (a setof V1_x and V1_y) by the processing denoted byV1_x=Vjs_x+Vb_cmd_by_ofs_x and V1_y=Vjs_y+Vb_cmd_by_ofs_y.

Further, the center of gravity desired velocity determiner 32 carriesout the processing by a processor 32 e. The processor 32 e carries outlimiting for determining a restricted center of gravity desired velocityVb_cmd_xy (a set of Vb_cmd_x and Vb_cmd_y) as a desired velocity of thevehicle system total center of gravity obtained by restricting thecombination of desired velocities V1_x and V1_y in order to prevent therotational speed of each of the electric motors 8 a and 8 b constitutingthe actuator 8 of the first travel operation unit 3 from deviating froma predetermined permissible range.

In this case, if the set of the desired velocities V1_x and V1_ydetermined by the processor 32 d lies within a predetermined region(e.g., an octagonal region) on a coordinate system, in which the axis ofordinate indicates the value of the desired velocity V1_x and the axisof abscissa indicates the value of the desired velocity V1_y, then thedesired velocity V1_xy is determined directly as the restricted centerof gravity desired velocity Vb_cmd_xy.

Further, if the set of the desired velocities V1_x and V1_y determinedby the processor 32 d deviates from the predetermined region on thecoordinate system, then a set that has been restricted to lie on theboundary of the predetermined region is determined as the restrictedcenter of gravity desired velocity Vb_cmd_xy.

The center of gravity desired velocity Vb_cmd_xy is determined on thebasis of the basic velocity command Vjs_xy and the center of gravityoffset influence amount Vofs_xy (or the center of gravity offset) asdescribed above. This enables the rider to maneuver the vehicle 1 byoperating the operation device, i.e., by operating the joystick 12, andby changing the posture of his/her body, i.e., by shifting his/herweight.

After carrying out the processing by the center of gravity desiredvelocity determiner 32, the first control processor 24 carries out theprocessing by the posture control arithmetic unit 34. The posturecontrol arithmetic unit 34 carries out the processing illustrated by theblock diagram of FIG. 4 to determine a first desired velocityVw1_cmd_xy, which is the desired value of the travel velocity(translational velocity) of the first travel operation unit 3.

More specifically, the posture control arithmetic unit 34 first carriesout, by the arithmetic unit 34 b, the processing for subtracting eachcomponent of the center of gravity offset influence amount Vofs_xy fromeach component of the restricted center of gravity desired velocityVb_cmd_xy, thereby determining a desired velocity with a compensatedcenter of gravity offset Vb_cmpn_cmd_xy (a latest value).

Subsequently, according to expressions (4a) and (4b) given below, theposture control arithmetic unit 34 calculates a desired translationalacceleration in the X-axis direction DVw1_cmd_x and a desiredtranslational acceleration in the Y-axis direction DVw1_cmd_y of adesired translational acceleration DVw1_cmd_xy, which is the desiredvalue of the translational acceleration at the ground contact point ofthe first travel operation unit 3, by carrying out the processingthrough the arithmetic units except for the arithmetic unit 34 b and anintegral arithmetic unit 34 a, which carries out integral operations.

DVw1_cmd_(—) x=Kvb _(—) x·(Vb_cmpn_cmd_(—) x−Vb_estm1_(—) x)−Kth _(—)x·θb_act_(—) x−Kw _(—) x·ωb_act_(—) x  (4a)

DVw1_cmd_(—) y=Kvb _(—) y·(Vb_cmpn_cmd_(—) y−Vb_estm1_(—) y)−Kth _(—)y·θb_act_(—) y−Kw _(—) y·ωb_act_(—) y  (4b)

In expressions (4a) and (4b), Kvb_xy, Kth_xy and Kw_xy denotepredetermined gain values set beforehand.

The first term of the right side of expression (4a) denotes a feedbackmanipulated variable component based on the difference between thecompensated center of gravity offset desired velocity in the X-axisdirection Vb_cmpn_cmd_x (a latest value) of the vehicle system totalcenter of gravity and a first estimated value Vb_estm1_x (a latestvalue), the second term thereof denotes a feedback manipulated variablecomponent based on a measurement value (a latest value) of an actualtilt angle in the direction about the Y-axis θb_act_x of the ridermounting section 5, and the third term thereof denotes a feedbackmanipulated variable component based on a measurement value (a latestvalue) of an actual tilt angular velocity in the direction about theY-axis ωb_act_x of the rider mounting section 5. Further, a desiredtranslational acceleration in the X-axis direction DVw1_cmd_x iscalculated as a resultant manipulated variable of the above feedbackmanipulated variable components.

Similarly, the first term of the right side of expression (4b) denotes afeedback manipulated variable component based on the difference betweenthe compensated center of gravity-offset desired velocity in the Y-axisdirection Vb_cmpn_cmd_y (a latest value) of the vehicle system totalcenter of gravity and a first estimated value Vb_estm1_y (a latestvalue), the second term thereof denotes a feedback manipulated variablecomponent based on a measurement value (a latest value) of an actualtilt angle in the direction about the X-axis θb_act_y of the ridermounting section 5, and the third term thereof denotes a feedbackmanipulated variable component based on a measurement value (a latestvalue) of an actual tilt angular velocity in the direction about theX-axis ωb_act_y of the rider mounting section 5. Further, a desiredtranslational acceleration in the Y-axis direction DVw1_cmd_y iscalculated as a resultant manipulated variable of the above feedbackmanipulated variable components.

Subsequently, the posture control arithmetic unit 34 integrates thecomponents of the desired translational acceleration DVw1_cmd_xy by theintegral arithmetic unit 34 a, thereby determining a first desiredvelocity Vw1_cmd_xy (a latest value) of the first travel operation unit3.

Then, the first control processor 24 controls the electric motors 8 aand 8 b constituting the actuator 8 of the first travel operation unit 3according to the first desired velocity Vw1_cmd_xy determined asdescribed above. More specifically, the first control processor 24determines the current command values for the electric motors 8 a and 8b by feedback control processing so as to make the actual rotationalvelocities (measurement values) of the electric motors 8 a and 8 bfollow the desired values of the rotational velocities thereof specifiedby the first desired velocity Vw1_cmd_xy. The first control processor 24then energizes the electric motors 8 a and 8 b according to the currentcommand values.

In a state wherein the restricted center of gravity desired velocityVb_cmd_xy remains at a fixed value and the motion of the vehicle 1 hasbeen stabilized after the aforesaid processing, i.e., in a state whereinthe vehicle 1 is traveling in a straight line at a fixed velocity, thevehicle system total center of gravity lies right above the groundcontact point of the first travel operation unit 3. In this state, theactual tilt angle θb_act_xy of the rider mounting section 5 will be−Ofst_xy/(h−r_xy) according to expressions (1b) and (2b). The actualtilt angular velocity ωb_act_xy of the rider mounting section 5 will bezero and the desired translational acceleration DVw1_cmd_xy will bezero. This combined with the block diagram of FIG. 4 lead to the findingof the agreement between Vb_estm1_xy and Vb_cmd_xy.

In other words, the first desired velocity Vw1_cmd_xy of the firsttravel operation unit 3 is basically determined to converge thedifference between the restricted center of gravity desired velocityVb_cmd_xy of the vehicle system total center of gravity and the firstestimated value Vb_estm1_xy to zero.

Further, the rotational speeds of the electric motors 8 a and 8 bconstituting the actuator 8 of the first travel operation unit 3 arecontrolled so as not to deviate from a predetermined permissible rangeby the processing carried out by the processor 32 e while compensatingfor the influence on the deviation of the position of the vehicle systemtotal center of gravity from the position of the reference portion Ps_xyin the inverted pendulum model.

Supplementarily, in expressions (4a) and (4b) given above,Vb_cmpn_cmd_x=Vb_cmd_x−Vofs_x=Vb_cmd_x−(Kth/h−r_x)·(1/Kvb)·Ofst_estm_xandVb_cmpn_cmd_y=Vb_cmd_y−Vofs_y=Vb_cmd_y−(Kth/h−r_y)·(1/Kvb)·Ofst_estm_y.Therefore, expressions (4a) and (4b) can be rewritten to expressions(4a)′ and (4b)′, respectively, given below.

DVw1_cmd_(—) x=Kvb·(Vb_cmd_(—) x−Vb_estm1_(—) x)−Kth·(Ofst_estm_(—)x/(h−r _(—) x)+θb_act_(—) x)−Kw _(—) x·ωb_act_(—) x  (4a)′

DVw1_cmd_(—) y=Kvb·(Vb_cmd_(—) y−Vb_estm1_(—) y)−Kth·(Ofst_estm_(—)y/(h−r _(—) y)+θb_act_(—) y)−Kw _(—) y·ωb_act_(—) y  (4b)′

In this case, the second term on the right side of each of expressions(4a)′ and (4b)′ denotes a feedback manipulated variable for setting theposition of the actual vehicle system total center of gravity in theX-axis direction and the Y-axis direction to a position right above theground contact portion of the first travel operation unit 3.

This completes the detailed description of the processing by the firstcontrol processor 24 in the present embodiment.

The processing by the second control processor 25 will now be describedwith reference to FIG. 8. To summarize the processing by the secondcontrol processor 25, the second processor 25 determines if there is arequest for turning the vehicle 1 (hereinafter referred to “the requestfor turning”) or the level of the request for turning on the basis of anactual motional state or a desired motional state of the representativepoint of the vehicle 1 of the vehicle system total center of gravity orthe like or the first travel operation unit 3 in the Y-axis direction(the lateral direction relative to the rider), or the motional state ofthe rider in relation to the aforesaid motional state.

According to the present embodiment, the estimated value Vb_estm1_y ofthe travel velocity of the vehicle system total center of gravity in theY-axis direction calculated by the center of gravity velocity estimator33 is used as an indicator for determining whether there is the requestfor turning or the level of the request for turning. Vb_estm1_ycoincides with the travel velocity of the reference portion Ps_y in theY-axis direction, so that it means the observed value of the travelvelocity of the representative point in the Y-axis direction, therepresentative point being fixed relative to the rider mounting section5 (or the base body 2).

If the second control processor 25 determines that there is the requestfor turning, then it decides a second desired velocity in the Y-axisdirection Vw2_cmd_y of the second travel operation unit 4 such that theVw2_cmd_y is different from a first desired velocity in the Y-axisdirection Vw1_cmd_y of the first travel operation unit 3 so as to makethe vehicle 1 turn.

To be more specific, the second control processor 25 carries out theaforesaid processing as follows. Referring to FIG. 8, the second controlprocessor 25 first carries out the processing by a processor 41. Theprocessor 41 receives the estimated value Vb_estm1_y (a latest value) ofthe travel velocity of the vehicle system total center of gravity in theY-axis direction calculated by the center of gravity velocity estimator33. The processor 41 then decides a dead zone processed velocity Vw1a_yon the basis of the Vb_estm1_y.

When the rider on the vehicle 1 wishes to turn the vehicle 1 to theright or left, the rider usually tilts his/her upper body to the rightor left so as to shift his/her center of gravity to the right or leftrelative to the vehicle 1. At this time, the first desired velocityVw1_cmd_y in the lateral direction of the first travel operation unit 3determined by the control processing by the first control processor 24will basically become a rightward or leftward travel velocity.

However, even when the rider does not intend to turn the vehicle 1,there are some cases where the upper body of the rider accidentallysways, causing the center of gravity of the rider to slightly shift tothe right or left.

Hence, the processor 41 determines the dead zone processed velocityVw1a_y on the basis of Vb_estm1_y according to the characteristicsillustrated in the graph of FIG. 8. More specifically, if the absolutevalue of Vb_estm1_y is relatively small and Vb_estm1_y takes a valuewithin a predetermined range Δa around zero (if the absolute value ofVb_estm1_y is a predetermined value or less), then the processor 41regards that there is no request for turning and sets Vw1a_y to zero.

On the other hand, if the absolute value of Vb_estm1_y is relativelylarge and Vb_estm1_y takes a value out of the predetermined range Δa (ifthe absolute value of Vb_estm1_y is larger than the predeterminedvalue), then the processor 41 regards that there is the request forturning and sets Vw1a_y to a non-zero value.

More specifically, the processor 41 determines Vw1a_y on the basis ofVb_estm1_y such that the absolute value of Vw1a_y increases to apredetermined upper limit value or less as the absolute value ofVb_estm1_y increases. In this case, the polarity (direction) of Vw1a_yis to be the same as that of Vb_estm1_y. As will be discussed later, theincreasing rate of Vw1a_y with respect to the increase in Vb_estm1_y ispreferably one in order to set the center of turning to a desiredposition. In other words, the inclination is preferably one in an areaexcluding the dead zone and the saturation area in the graph of FIG. 8.

The parenthesized characters at the input end of the processor 41 inFIG. 8 relate to the modifications, which will be discussed later.

Subsequently, the second processor 25 carries out the processing by aprocessor 42. The processor 42 divides Vw1a_y by a distance L3 in theX-axis direction between the ground contact portion of the first traveloperation unit 3 and the center of turn. Thus, the processor 42determines a desired turn angular velocity ωz_cmd_gc, which is thedesired value of the turn angular velocity (the angular velocity in thedirection about the yaw axis) of the vehicle 1. In this case, theprocessor 42 sets the distance L3 on the basis of the estimated value ofthe actual travel velocity in the X-axis direction Vb_estm1_x (a latestvalue) of the vehicle system total center of gravity, which is therepresentative point of the vehicle 1.

The center of turn more specifically means the center of turning in thedirection about the yaw axis of the entire vehicle 1 observed in acoordinate system that translatorily travels together with the firsttravel operation unit 3 on a floor surface.

In the present embodiment, the vehicle 1 is turned such that the vehicle1 turns in the direction about the yaw axis, using, as the center ofturning, a point on a floor surface at the rear side of the groundcontact portion of the first travel operation unit 3 (i.e., behind therider on the rider mounting section 5). If Vb_estm1_x is zero, then thedistance L3 in the X-axis direction between the center of turning andthe ground contact portion of the first travel operation unit 3 is setsuch that the center of turning is positioned in the vicinity of theground contact portion of the second travel operation unit 4. Forexample, L3 is set to coincide or substantially coincide with thedistance between the ground contact portion of the first traveloperation unit 3 and the ground contact portion of the second traveloperation unit 4.

If Vb_estm1_x is positive, which means traveling forward, then L3 is setsuch that the center of turning moves toward the ground contact portionof the first travel operation unit 3 from the ground contact portion ofthe second travel operation unit 4, i.e., the position of the center ofturning in the X-axis direction approaches the position right under therider sitting on the rider mounting section 5 (the position of the riderprojected onto a floor surface). In other words, L3 is set such that L3decreases as the magnitude (absolute value) of Vb_estm1_x increases.However, L3 is limited to a distance equal to or more than apredetermined lower limit value (>0).

If Vb_estm1_x is negative, which means traveling backward, then L3 ispreferably set to the same value as that set in the case whereVb_estm1_x is zero or set such that L3 increases as the magnitude(absolute value) of Vb_estm1_x increases.

The processor 42 determines the desired turn angular velocity ωz_cmd_gcby dividing Vw1a_y by the distance L3 determined on the basis ofVb_estm1_x. The desired turn angular velocity ωz_cmd_gc is a left hand(counterclockwise) angular velocity in the case where Vw1a_y is aleftward velocity, while it is a right hand (clockwise) angular velocityin the case where Vw1a_y is a rightward velocity.

Subsequently, the second control processor 25 carries out the processingby a processor 43. The processor 43 multiplies the desired turn angularvelocity ωz_cmd_gc determined by the processor 42 by a value that is(−1) times the predetermined distance L between the ground contactportion of the first travel operation unit 3 and the ground contactportion of the second travel operation unit 4 (=−L). Thus, the processor43 calculates a relative travel velocity in the Y-axis directionΔVw2_cmd_y of the second travel operation unit 4 with respect to thefirst travel operation unit 3 in the case where the vehicle 1 is turnedat the desired turn angular velocity ωz_cmd_gc.

The relative travel velocity in the Y-axis direction ΔVw2_cmd_y of thesecond travel operation unit 4 determined as described above becomeszero in the case where ωz_cmd_gc=0 (i.e., in the case where there is norequest for turning). Further, ΔVw2_cmd_y becomes a rightward velocityin the case where ωz_cmd_gc is a leftward turn angular velocity and itbecomes a leftward velocity in the case where ωz_cmd_gc is a rightwardturn angular velocity. Hence, ΔVw2_cmd_y in the case where there is therequest for turning is a velocity in the opposite direction from Vw1a_yor Vb_estm1_y.

Subsequently, the second control processor 25 carries out the processingby a processor 44. The processor 44 adds the relative travel velocity inthe Y-axis direction ΔVw2_cmd_y of the second travel operation unit 4 tothe first desired velocity in the Y-axis direction Vw1_cmd_y (a latestvalue) of the first travel operation unit 3 determined by the firstcontrol processor 24. Thus, the processor 44 determines a basic valueVw2_cmda_y (a latest value) of the second desired velocity in the Y-axisdirection Vw2_cmd_y of the second travel operation unit 4.

Subsequently, the second control processor 25 carries out the processingby a processor 45. The processor 45 carries out slippage preventionprocessing for preventing slippage of the second travel operation unit 4so as to determine the second desired velocity in the Y-axis directionVw2_cmd_y of the second travel operation unit 4.

In this case, if it is predicted that the slippage of the second traveloperation unit 4 is likely to happen due to, for example, an excessivelylarge absolute value of the basic value Vw2_cmda_y, then the processor45 sets the second desired velocity in the Y-axis direction Vw2_cmd_y ofthe second travel operation unit 4 to a velocity corrected over thebasic value Vw2_cmda_y. If it is predicted that the slippage of thesecond travel operation unit 4 will not happen, then the processor 45directly determines the basic value Vw2_cmda_y as the second desiredvelocity in the Y-axis direction Vw2_cmd_y of the second traveloperation unit 4.

The processing by the processor 45 may be omitted if a sufficientfrictional force between the second travel operation unit 4 and a floorsurface is secured by, for example, pressing the second travel operationunit 4 against the floor surface by a spring or the like.

Then, the second control processor 25 controls the electric motor 17,which acts as the actuator of the second travel operation unit 4,according to the second desired velocity Vw2_cmd_xy determined asdescribed above. More specifically, the second control processor 25determines a current command value for the electric motor 17 by feedbackcontrol processing so as to make the actual rotational speed (measuredvalue) follow the desired value of the rotational speed of the electricmotor 17 specified by the second desired velocity Vw2_cmd_xy. Then, thesecond control processor 25 energizes the electric motor 17 according tothe current command value.

The control processing by the second control processor 25 is carried outas described above. Thus, the second desired velocity in the Y-axisdirection Vw2_cmd_y of the second travel operation unit 4 is basicallydetermined to be the velocity obtained by adding the relative travelvelocity ΔVw2_cmd_y to the first desired velocity in the Y-axisdirection Vw1_cmd_y (a latest value) of the first travel operation unit3.

In this case, if it is determined that the absolute value of theestimated value of the travel velocity in the Y-axis directionVb_estm1_y of the vehicle system total center of gravity is sufficientlysmall and there is no request for turning, then ΔVw2_cmd_y will be zero(ΔVw2_cmd_y=0). Hence, the second desired velocity in the Y-axisdirection Vw2_cmd_y of the second travel operation unit 4 is basicallydetermined to coincide with the first desired velocity in the Y-axisdirection Vw1_cmd_y of the first travel operation unit 3.

Meanwhile, if it is determined that the absolute value of the estimatedvalue of the travel velocity in the Y-axis direction Vb_estm1_y of thevehicle system total center of gravity is relatively large and there isthe request for turning, then ΔVw2_cmd_y will be determined to be avelocity in the opposite direction from that of Vb_estm1_y. Hence, thesecond desired velocity in the Y-axis direction Vw2_cmd_y of the secondtravel operation unit 4 is basically determined to be a velocity whichis in the same direction as the first desired velocity in the Y-axisdirection Vw1_cmd_y of the first travel operation unit 3 and which issmaller than Vw1_cmd_y (a zero velocity or a velocity close to zero), ordetermined to be a velocity which is in the opposite direction from thatof the first desired velocity in the Y-axis direction Vw1_cmd_y of thefirst travel operation unit 3.

The vehicle 1 according to the present embodiment described aboveenables the translational travel of the vehicle 1 in the X-axisdirection to be accomplished according to the travel forward/backwardcommand output in response to a longitudinal tilt (in the X-axisdirection) of the rider mounting section 5 (or the base body 2) causedby the movement of the body of the rider on the rider mounting section 5or in response to the operation of swinging the joystick 12 in thelongitudinal direction.

In a situation wherein the lateral movement of the center of gravity ofthe rider on the rider mounting section 5 (the relative movement withrespect to the rider mounting section 5) is relatively small and theestimated value of the travel velocity in the Y-axis directionVb_estm1_y of the vehicle system total center of gravity falls within apredetermined range Δa in the vicinity of zero, the translational travelof the vehicle 1 in the Y-axis direction can be accomplished accordingto the lateral travel command issued in response to a small tilt of therider mounting section 5 (or the base body 2) in the lateral direction(the Y-axis direction) or in response to the swinging of the joystick 12in the lateral direction.

Further, combining the aforesaid translational travels enables thevehicle 1 to translatorily travel in an arbitrary direction at an anglerelative the X-axis direction and the Y-axis direction.

If the estimated value of the travel velocity in the Y-axis directionVb_estm1_y of the vehicle system total center of gravity deviates fromthe predetermined range Δa in the vicinity of zero due to a relativelylarge lateral movement of the center of gravity of the rider on therider mounting section 5, then the second desired velocity in the Y-axisdirection Vw2_cmd_y of the second travel operation unit 4 is determinedto be a velocity obtained by shifting the first desired velocity in theY-axis direction Vw1_cmd_y of the second travel operation unit 4 byΔVw2_cmd_y. In this case, the second desired velocity Vw2_cmd_y isdetermined to be a velocity that causes the vehicle 1 to turn about thecenter of turning at the rear side of the ground contact portion of thefirst travel operation unit 3.

This enables the rider to turn the vehicle 1 simply by moving his/herupper body to move his/her center of gravity in the lateral direction.In this case, if the rider moves his/her center of gravity to the left,then the vehicle 1 turns to the left. If the rider moves his/her centerof gravity to the right, then the vehicle 1 turns to the right. Thus,the movement of the center of gravity of the rider in the lateraldirection matches the turning direction of the vehicle 1.

Hence, the rider can easily turn the vehicle 1 by moving his/her upperbody in the lateral direction and also easily learn the steeringoperation for turning the vehicle 1.

If, for example, the rider attempts to turn (change the direction of)the vehicle 1 while the vehicle 1 is in a stopped state (i.e., thetravels of the first travel operation unit 3 and the second traveloperation unit 4 have substantially finished), then the first traveloperation unit 3 supporting the weight of the rider and the weight ofthe majority of the vehicle 1 will move in the lateral direction, i.e.,the Y-axis direction. Hence, it is possible to prevent a largefrictional force from being applied to the first travel operation unit3. This permits smooth turning (or direction changing) of the vehicle 1.

Further, when the rider intends to turn the vehicle 1 while moving thevehicle 1 forward (in the positive direction of the X-axis), thedistance L3 between the ground contact portion of the first traveloperation unit 3 and the center of turning decreases as the magnitude(absolute value) of the estimated value of the travel velocity in theX-axis direction of the vehicle system total center of gravity servingas the representative point of the vehicle 1 increases. This enables therider to easily set the traveling trajectory at the time of turning ofthe vehicle 1 to a desired trajectory.

Further, in the present embodiment, the center of gravity offsetestimator 35 a of the first control processor 24 estimates the center ofgravity offset amount Ofst_xy of the vehicle system total center ofgravity by carrying out the processing illustrated in FIG. 7. Thispermits highly accurate estimation of the center of gravity offsetamount. Then, the desired velocity of the vehicle system total center ofgravity (the restricted desired velocity of the center of gravity)Vb_cmd_xy is determined as described above on the basis of the estimatedvalue Ofst_estm_xy of the center of gravity offset amount Ofst_xy. Thus,the influence exerted by the center of gravity offset amount Ofst_xy onthe behavior of the vehicle 1 can be properly compensated for.

Moreover, in the vehicle 1 according to the present embodiment, theswing amount (the amount of swing in the direction about the Y-axis) ofthe second travel operation unit 4 relative to the base body 2 ismechanically restricted to a predetermined range defined by the stoppers16 and 16. This arrangement makes it possible to prevent especially therider mounting section 5 from excessively inclining to the rear side ofthe rider.

Second Embodiment and Third Embodiment

A second and a third embodiments according to the present invention willnow be described with reference to FIG. 9A and FIG. 9B. The second andthe third embodiments differ from the first embodiment only partly inthe processing carried out by the second control processor 25. In thedescription of the second and the third embodiments, the description ofthe same aspects as those of the first embodiment will be omitted.

The parenthesized characters in FIG. 9A and FIG. 9B relate tomodifications to be discussed hereinafter.

FIG. 9A illustrates the processing carried out by a second controlprocessor 25 to determine Vw1a_y (the desired value of a dead zoneprocessed velocity) on the basis of the estimated value of the travelvelocity in the Y-axis direction Vb_estm1_y of the vehicle system totalcenter of gravity in the second embodiment.

In the second embodiment, the second control processor 25 has a low cutfilter (pseudo differential filter) 51 to which the estimated value ofthe travel velocity in the Y-axis direction Vb_estm1_y of the vehiclesystem total center of gravity is supplied. The second control processor25 adds a value, which is obtained by multiplying an output of a low cutfilter 51 (a value obtained by subjecting Vb_estm1_y to a low cutcharacteristic filtering) by a gain Kd of a predetermined value in aprocessor 52, to Vb_estm1_y by an arithmetic unit 53.

Subsequently, the second control processor 25 inputs the output of thearithmetic unit 53 instead of Vb_estm1_y to a processor 41, which is thesame as that in the first embodiment, and carries out the processing bythe processing 41 in the same manner as that in the first embodiment,thereby determining Vw1a_y. In other words, Vw1a_y corresponds to aresult obtained by processing Vb_estm1_y through a phase compensationcircuit (filter).

The second embodiment is the same as the first embodiment except for theaspects described above.

According to the second embodiment described above, Vw1a_y and thereforethe desired turn angular velocity ωz_cmd_gc are determined on the basisof the phase compensation value (the output of the arithmetic unit 53)of the estimated value of the travel velocity in the Y-axis directionVb_estm1_y of the vehicle system total center of gravity and an outputof the low-cut filter 51 based on the temporal change rate thereof.

This arrangement makes it possible to improve the responsiveness of theturning behavior of the vehicle 1 relative to the movement of thevehicle system total center of gravity in the Y-axis directionattributable to the movement of the upper body of the rider.

FIG. 9B illustrates the processing carried out by a second controlprocessor 25 to determine Vw1a_y (the desired value of a dead zoneprocessed velocity) on the basis of the estimated value of the travelvelocity in the Y-axis direction Vb_estm1_y of the vehicle system totalcenter of gravity in the third embodiment.

In the third embodiment, as with the first embodiment, the estimatedvalue of the travel velocity in the Y-axis direction Vb_estm1_y of thevehicle system total center of gravity is supplied to a processor 41.

Further, the second control processor 25 according to the thirdembodiment is provided with a processor 54, which receives an output ofa processor 52, in addition to the same low cut filter 51 and processor52 as those in the second embodiment. The processor 54 carries outprocessing similar to the processing carried out by the processor 41.

To be more specific, if the absolute value of an input value of theprocessor 54 is relatively small and the input value falls within apredetermined range Δb around zero (if the absolute value of the inputvalue is a predetermined value or less), then the processor 54 sets anoutput value to zero.

Conversely, if the absolute value of an input value of the processor 54is relatively large and therefore the input value deviates from thepredetermined range Δb (if the absolute value of the input value islarger than the predetermined value), then the processor 54 sets anoutput value to a non-zero value.

To be more specific, the processor 54 determines an output value on thebasis of an input value of the processor 54 such that the absolute valueof the output value increases to a predetermined upper limit value orless as the absolute value of the input value of the processor 54increases. In this case, the polarity (direction) of the output value ofthe processor 54 is to be the same as that of the input value.

Then, the second processor 25 in the third embodiment adds up the outputvalue of the processor 41 and the output value of the processor 54 by anarithmetic unit 55 so as to determine Vw1a_y.

The third embodiment is the same as the first embodiment except for theaspects described above.

According to the third embodiment, Vw1a_y is determined by adding up acomponent determined by the processor 41 on the basis of the estimatedvalue of the travel velocity in the Y-axis direction Vb_estm1_y of thevehicle system total center of gravity and a component determined by theprocessor 54 on the basis of the output of the low cut filter 51, whichdepends on the temporal change rate of Vb_estm1_y.

Thus, as with the second embodiment, the third embodiment permitsimproved responsiveness of the turning behavior of the vehicle 1relative to the movement of the vehicle system total center of gravityin the Y-axis direction caused by the movement of the upper body of therider.

[Modifications]

A few modifications of the embodiments described above will now bedescribed.

According to the embodiments described above, in the processing by thesecond control processor 25, the estimated value of the travel velocityin the Y-axis direction Vb_estm1_y of the vehicle system total center ofgravity calculated by the center of gravity velocity estimator 33 hasbeen used as the indicator for determining whether there is the requestfor turning or the level of the request for turning. Alternatively,however, a parameter other than Vb_estm1_y may be used as the indicatorfor determining whether there is the request for turning or the level ofthe request for turning.

For example, the desired turn angular velocity ωz_cmd_gc of the vehicle1 may be determined by carrying out the processing by the processors 41and 42, as with the aforesaid embodiments by using the center of gravityoffset influence amount in the Y-axis direction Vofs_y (or an estimatedvalue of the center of gravity offset amount Ofst_estm_y) calculated bya center of gravity offset influence amount calculator 35 b of the firstcontrol processor 24, or a restricted velocity command in the Y-axisdirection V2_y determined by a processor 32 e, a first desired velocityin the Y-axis direction Vw1_cmd_y of the first travel operation unit 3determined by a posture control arithmetic unit 34, or an observed valueof an actual travel velocity in the Y-axis direction Vw1_act_y of thefirst travel operation unit 3 (e.g., the value of Vw1_act_y estimatedfrom a detected value of the rotational speed of the electric motor 8b), in place Vb_estm1_y, as indicated by the parenthesized referencecharacters in FIG. 8 or FIG. 9A or FIG. 9B.

In this case, in the processor 41, a range Δa of the value of an inputparameter that sets an output value thereof to zero (the magnitudes ofthe upper limit value and the lower limit value of the range Δa) and thechange rate of an output value relative to a change in the value of theinput parameter that is out of the range Δa is usually set for each typeof input parameter. The same applies to the processor 54 shown in FIG.9B.

Even in the case where the aforesaid parameters are used in place ofVb_estm1_y, the vehicle 1 can be turned according to the movement of theupper body of the rider in the lateral direction, as with theembodiments described above.

In the case where the center of gravity offset influence amount in theY-axis direction Vofs_y calculated by the center of gravity offsetinfluence amount calculator 35 b of the first control processor 24 isused in place of Vb_estm1_y, the Vofs_y is proportional to the estimatedvalue of the center of gravity offset amount in the Y-axis directionOfst_estm_y. Accordingly, setting the desired turn angular velocityωz_cmd_gc of the vehicle 1 on the basis of Vofs_y is equivalent tosetting the desired turn angular velocity ωz_cmd_gc of the vehicle 1 onthe basis of the estimated value of the center of gravity offset amountin the Y-axis direction Ofst_estm_y.

Hence, an embodiment according to the aforesaid tenth aspect of theinvention is created by using Vofs_y in place of Vb_estm1_y. In thiscase, the center of gravity offset estimator 32 a corresponds to thetotal center of gravity offset estimating unit in the tenth aspect ofthe invention, and Ofst_estm_y corresponds to the lateral total centerof gravity offset amount in the sixth aspect of the invention. In thiscase, even if the lateral travel command is output by the joystick 12,no turn based on the command will take place.

Further, in the embodiments described above, the distance L3 between thecenter of turning and the ground contact portion of the first traveloperation unit 3 at the time of turning of the vehicle 1 has beenchanged on the basis of the estimated value (observed value) of thetravel velocity in the longitudinal direction Vb_estm_x of the vehiclesystem total center of gravity. Alternatively, however, L3 may be set toa fixed value established beforehand.

Further, in the first embodiment, the desired turn angular velocityωz_cmd_gc has been set to zero in the case where the estimated value ofthe travel velocity in the Y-axis direction Vb_estm1_y of the vehiclesystem total center of gravity, which is an input parameter of theprocessor 41, is a value within the predetermined range Δa in thevicinity of zero. Alternatively, however, the desired turn angularvelocity ωz_cmd_gc may be set to cause the vehicle 1 to turn even whenthe input parameter falls within the predetermined range Δa. In otherwords, Δa may be set to zero.

Further, in the embodiments described above, the second travel operationunit 4 has been disposed behind the first travel operation unit 3.Alternatively, however, the second travel operation unit 4 may bedisposed in front of the first travel operation unit 3. In this case,the turning of the vehicle 1 can be accomplished by setting the travelvelocity in the Y-axis direction of the second travel operation unit 4to be larger than the travel velocity in the Y-axis direction of thefirst travel operation unit 3 at the time of turning.

In the embodiments described above, the joystick 12 has been used as theoperation device for outputting the forward/backward travel command andthe lateral travel command. Alternatively, however, a trackball or atouch-pad may be used in place of a joystick, or a load sensor adaptedto detect a place touched by a rider or a posture sensor held by a ridermay be used. Further alternatively, a portable terminal, such as asmartphone, may be used as the operation device.

Further, the operation device, such as the joystick 12, may be omittedor an operation device that outputs only the forward/backward travelcommand may be provided.

Further, the second travel operation unit 4 may have a configurationother than the omniwheel and may have, for example, the sameconfiguration as that of the first travel operation unit 3.

Further alternatively, an arrangement may be adopted such that a riderselectively operates selector switches or the like to switch between amode in which the rider moves his/her body in the lateral directionthereby to turn the vehicle 1 and a mode in which the rider operates anoperation device, such as a joystick, to turn the vehicle 1.

What is claimed is:
 1. An inverted pendulum type vehicle having at leasta first travel operation unit capable of traveling on a floor surface; afirst actuator that drives the first travel operation unit; a base bodyto which the first travel operation unit and the first actuator areinstalled; and a rider mounting section attached to the base body suchthat the rider mounting section is tiltable relative to a verticaldirection, wherein the first travel operation unit is configured to becapable of traveling in all directions, including a longitudinaldirection and a lateral direction relative to a rider on the ridermounting section, by a driving force of the first actuator, the invertedpendulum type vehicle comprising: a second travel operation unit, whichis connected to the first travel operation unit or the base body with aninterval provided from the first travel operation unit in thelongitudinal direction and which is configured to be capable oftraveling in all directions on a floor surface; a second actuator whichgenerates a driving force for causing the second travel operation unitto travel at least in the lateral direction; and a control unit, whichcontrols the first actuator and the second actuator so as to cause thefirst travel operation unit and the second travel operation unit tocarry out travel motions thereof according to at least the tilt of therider mounting section, wherein the control unit is configured to carryout turning control processing for controlling, through the firstactuator and the second actuator, a travel velocity of the first traveloperation unit and a travel velocity of the second travel operation unitin the lateral direction to be different from each other so as to causethe inverted pendulum type vehicle to turn about a turn center behind aground contact point of the first travel operation unit in a situationin which a predetermined representative point of the inverted pendulumtype vehicle that has been established beforehand or the first traveloperation unit is to be moved leftward or rightward.
 2. The invertedpendulum type vehicle according to claim 1, wherein the second traveloperation unit is disposed at the rear of the first travel operationunit.
 3. The inverted pendulum type vehicle according to claim 1,wherein the control unit is configured to control, through the firstactuator and the second actuator, the travel velocity of the firsttravel operation unit and the travel velocity of the second traveloperation unit in the lateral direction on the basis of a desired valueor an observed value of the travel velocity of the predeterminedrepresentative point or the first travel operation unit in a forwarddirection such that a position of the turn center in the longitudinaldirection is moved toward a front at a rear side of the rider on therider mounting section as a magnitude of the desired value or theobserved value of the travel velocity of the predeterminedrepresentative point or the first travel operation unit in a forwarddirection increases in the turning control processing.
 4. The invertedpendulum type vehicle according to claim 1, wherein the control unit isconfigured to carry out the turning control processing in a situation inwhich a magnitude of a desired value or an observed value of theleftward or rightward travel velocity of the predeterminedrepresentative point or the first travel operation unit is apredetermined value or more and to control the first actuator and thesecond actuator such that the travel velocity of the first traveloperation unit and the travel velocity of the second travel operationunit in the lateral direction are the same with each other in asituation in which the magnitude of the desired value or the observedvalue of the travel velocity is smaller than a predetermined value. 5.The inverted pendulum type vehicle according to claim 4, wherein thecontrol unit carries out the turning control processing in a situationwherein the magnitude of the observed value of the velocity of therightward or leftward travel of the predetermined representative point,which has been set beforehand as a point fixed with respect to the ridermounting section, is a predetermined value or more.
 6. The invertedpendulum type vehicle according to claim 1, wherein the control unit isconfigured to determine a desired value of a turn angular velocity ofthe inverted pendulum type vehicle on the basis of at least a desiredvalue or an observed value of the velocity of the rightward or leftwardtravel of the predetermined representative point or the first traveloperation unit and to control the velocities of the travels of the firsttravel operation unit and the second travel operation unit in thelateral direction on the basis of the desired value of the turn angularvelocity through the first actuator and the second actuator,respectively, in the turning control processing.
 7. An inverted pendulumtype vehicle having at least a first travel operation unit capable oftraveling on a floor surface, a first actuator that drives the firsttravel operation unit, a base body to which the first travel operationunit and the first actuator are installed, and a rider mounting sectionattached to the base body such that the rider mounting section istiltable relative to a vertical direction, wherein the first traveloperation unit is configured to be capable of traveling in alldirections, including a longitudinal direction and a lateral directionrelative to a rider on the rider mounting section, by a driving force ofthe first actuator, the inverted pendulum type vehicle comprising: asecond travel operation unit, which is connected to the first traveloperation unit or the base body with an interval provided from the firsttravel operation unit in the longitudinal direction and which isconfigured to be capable of traveling in all directions on a floorsurface; a second actuator which generates a driving force for causingthe second travel operation unit to travel at least in the lateraldirection; and a control unit, which controls the first actuator and thesecond actuator so as to cause the first travel operation unit and thesecond travel operation unit to carry out travel motions thereofaccording to at least the tilt of the rider mounting section, whereinthe control unit is configured to carry out turning control processingfor controlling a travel velocity of the first travel operation unit anda travel velocity of the second travel operation unit in the lateraldirection through the first actuator and the second actuator,respectively, to differ from each other so as to cause the invertedpendulum type vehicle to turn about a turn center on a rear side of aground contact point of the first travel operation unit in a situationin which the rider on the rider mounting section has shifted his/hercenter of gravity to the right or left relatively with respect to therider mounting section.
 8. The inverted pendulum type vehicle accordingto claim 7, wherein the second travel operation unit is disposed on therear side of the first travel operation unit.
 9. The inverted pendulumtype vehicle according to claim 7, wherein the control unit isconfigured to control, through the first actuator and the secondactuator, the travel velocity of the first travel operation unit and thetravel velocity of the second travel operation unit in the lateraldirection on the basis of a desired value or an observed value of thetravel velocity in a forward direction of the predeterminedrepresentative point or the first travel operation unit such that aposition of the turn center in the longitudinal direction is movedtoward a front on a rear side of the rider on the rider mounting sectionas a magnitude of the desired value or the observed value of thevelocity of the travel of the predetermined representative point of theinverted pendulum type vehicle, which has been set beforehand, or thefirst travel operation unit in the forward direction increases, in theturning control processing.
 10. An inverted pendulum type vehicle havingat least a first travel operation unit capable of traveling on a floorsurface, a first actuator that drives the first travel operation unit, abase body to which the first travel operation unit and the firstactuator are installed, and a rider mounting section attached to thebase body such that the rider mounting section is tiltable relative to avertical direction, wherein the first travel operation unit isconfigured to be capable of traveling in all directions, including alongitudinal direction and a lateral direction relative to a rider onthe rider mounting section, by a driving force of the first actuator,the inverted pendulum type vehicle comprising: a second travel operationunit, which is connected to the first travel operation unit or the basebody with an interval provided from the first travel operation unit inthe longitudinal direction and which is configured to be capable oftraveling in all directions on a floor surface; a second actuator whichgenerates a driving force for causing the second travel operation unitto travel at least in the lateral direction; a control unit, whichcontrols the first actuator and the second actuator so as to cause thefirst travel operation unit and the second travel operation unit tocarry out travel motions thereof according to at least the tilt of therider mounting section; and a total center of gravity offset estimatingunit which estimates a lateral total center of gravity offset amount,which is an amount of a lateral relative movement of a total center ofgravity of the rider and the inverted pendulum type vehicle with respectto the rider mounting section, the lateral total center of gravityoffset amount being accrued due to the rider on the rider mountingsection having shifted his/her center of gravity to the right or leftrelatively with respect to the rider mounting section, wherein thecontrol unit is configured to carry out turning control processing forcontrolling a travel velocity of the first travel operation unit and atravel velocity of the second travel operation unit in the lateraldirection through the first actuator and the second actuator,respectively, on the basis of a lateral total center of gravity offsetamount estimated by the total center of gravity offset estimating unitso as to turn the inverted pendulum type vehicle about a turn center ona rear side of a ground contact point of the first travel operation unitin a situation in which the rider on the rider mounting section hasshifted his/her center of gravity to the right or left relatively withrespect to the rider mounting section.
 11. The inverted pendulum typevehicle according to claim 10, wherein the control unit is configured tocarry out the turning control processing in a situation, wherein amagnitude of an estimated value of the lateral total center of gravityoffset amount is a predetermined value or more, and to control the firstactuator and the second actuator such that the travel velocity of thefirst travel operation unit and the travel velocity of the second traveloperation unit in the lateral direction are the same with each other ina situation wherein the magnitude of the estimated value of the lateraltotal center of gravity offset amount is smaller than a predeterminedvalue.
 12. The inverted pendulum type vehicle according to claim 11,wherein the control unit is configured to determine a desired value of aturn angular velocity of the inverted pendulum type vehicle on the basisof at least the estimated value of the lateral total center of gravityoffset amount and to control the velocities of the travels of the firsttravel operation unit and the second travel operation unit in thelateral direction on the basis of the desired value of the turn angularvelocity through the first actuator and the second actuator,respectively, in the turning control processing.
 13. The invertedpendulum type vehicle according to claim 10, wherein the second traveloperation unit is disposed on the rear side of the first traveloperation unit.
 14. The inverted pendulum type vehicle according toclaim 10, wherein the control unit is configured to control, through thefirst actuator and the second actuator, the travel velocity of the firsttravel operation unit and the travel velocity of the second traveloperation unit, respectively, in the lateral direction on the basis of adesired value or an observed value of the travel velocity of apredetermined representative point or the first travel operation unit ina forward direction such that a position of the turn center in thelongitudinal direction is moved toward a front on a rear side of therider on the rider mounting section as a magnitude of the desired valueor the observed value of the travel velocity of the predeterminedrepresentative point of the inverted pendulum type vehicle, which hasbeen set beforehand, or the first travel operation unit in the forwarddirection increases, in the turning control processing.